Update macOS build-installer script comments for 3.10 and remove unused pre-10.5 vestiges. (GH-27253)

(cherry picked from commit 42205ee512159de62c01e202ff799d78fac9ac26)

Co-authored-by: Ned Deily <nad@python.org>

2 files changed, 74 insertions, 59 deletions

diff --git a/Mac/BuildScript/README.rst b/Mac/BuildScript/README.rst
index 94a6bb2..4f74e7d 100644
--- a/Mac/BuildScript/README.rst
+++ b/Mac/BuildScript/README.rst
@@ -19,33 +19,87 @@ Starting with macOS 10.15 Catalina, Gatekeeper now also requires
 that installer packages are submitted to and pass Apple's automated
 notarization service using the altool command.  To pass notarization,
 the binaries included in the package must be built with at least
-the macOS 10.9 SDK, mout now be signed with the codesign utility
+the macOS 10.9 SDK, must now be signed with the codesign utility,
 and executables must opt in to the hardened run time option with
 any necessary entitlements.  Details of these processes are
 available in the on-line Apple Developer Documentation and man pages.
 
-As of 3.8.0 and 3.7.7, PSF practice is to build one installer variants
-for each release.  Note that as of this writing, no Pythons support
-building on a newer version of macOS that will run on older versions
+A goal of PSF-provided (python.org) Python binaries for macOS is to
+support a wide-range of operating system releases with one set of
+binaries.  Currently, the oldest release supported by python.org
+binaries is macOS 10.9; it is still possible to build Python and
+Python installers on older versions of macOS but we not regularly
+test on those systems nor provide binaries for them.
+
+Prior to Python 3.9.1, no Python releases supported building on a
+newer version of macOS that will run on older versions
 by setting MACOSX_DEPLOYMENT_TARGET. This is because the various
-Python C modules do not yet support runtime testing of macOS
+Python C modules did not yet support runtime testing of macOS
 feature availability (for example, by using macOS AvailabilityMacros.h
-and weak-linking).  To build a Python that is to be used on a
-range of macOS releases, always build on the oldest release to be
-supported; the necessary shared libraries for that release will
-normally also be available on later systems, with the occasional
-exception such as the removal of 32-bit libraries in macOS 10.15.
-
-build-installer requires Apple Developer tools, either from the
+and weak-linking). To build a Python that is to be used on a
+range of macOS releases, it was necessary to always build on the
+oldest release to be supported; the necessary shared libraries for
+that release will normally also be available on later systems,
+with the occasional exception such as the removal of 32-bit
+libraries in macOS 10.15. For 3.9.x and recent earlier systems,
+PSF practice was to provide a "macOS 64-bit Intel installer" variant
+that was built on 10.9 that would run on macOS 10.9 and later.
+
+Starting with 3.9.1, Python fully supports macOS "weaklinking",
+meaning it is now possible to build a Python on a current macOS version
+with a deployment target of an earlier macOS system. For 3.9.1 and
+later systems, we provide a "macOS 64-bit universal2 installer"
+variant, currently build on macOS 11 Big Sur with fat binaries
+natively supporting both Apple Silicon (arm64) and Intel-64
+(x86_64) Macs running macOS 10.9 or later.
+
+The legacy "macOS 64-bit Intel installer" variant is expected to
+be retired prior to the end of 3.9.x support.
+
+build-installer.py requires Apple Developer tools, either from the
 Command Line Tools package or from a full Xcode installation.
 You should use the most recent version of either for the operating
 system version in use.  (One notable exception: on macOS 10.6,
 Snow Leopard, use Xcode 3, not Xcode 4 which was released later
-in the 10.6 support cycle.)
+in the 10.6 support cycle.) build-installer.py also must be run
+with recent versions of Python 3.x or 2.7. On older systems,
+due to changes in TLS practices, it may be easier to manually
+download and cache third-party source distributions used by
+build-installer.py rather than have it attempt to automatically
+download them.
+
+1.  universal2, arm64 and x86_64, for OS X 10.9 (and later)::
+
+        /path/to/bootstrap/python3 build-installer.py \
+            --universal-archs=universal2 \
+            --dep-target=10.9
+
+    - builds the following third-party libraries
+
+        * OpenSSL 1.1.1
+        * Tcl/Tk 8.6
+        * NCurses
+        * SQLite
+        * XZ
+        * libffi
+
+    - uses system-supplied versions of third-party libraries
+
+        * readline module links with Apple BSD editline (libedit)
+        * zlib
+        * bz2
+
+    - recommended build environment:
+
+        * Mac OS X 11 or later
+        * Xcode Command Line Tools 12.5 or later
+        * current default macOS SDK
+        * ``MACOSX_DEPLOYMENT_TARGET=10.9``
+        * Apple ``clang``
 
-1.  64-bit, x86_64, for OS X 10.9 (and later)::
+2.  legacy Intel 64-bit, x86_64, for OS X 10.9 (and later)::
 
-        /path/to/bootstrap/python2.7 build-installer.py \
+        /path/to/bootstrap/python3 build-installer.py \
             --universal-archs=intel-64 \
             --dep-target=10.9
 
diff --git a/Mac/BuildScript/build-installer.py b/Mac/BuildScript/build-installer.py
index 60174eb..56d3d4b 100755
--- a/Mac/BuildScript/build-installer.py
+++ b/Mac/BuildScript/build-installer.py
@@ -2,6 +2,10 @@
 """
 This script is used to build "official" universal installers on macOS.
 
+NEW for 3.10 and backports:
+- support universal2 variant with arm64 and x86_64 archs
+- enable clang optimizations when building on 10.15+
+
 NEW for 3.9.0 and backports:
 - 2.7 end-of-life issues:
     - Python 3 installs now update the Current version link
@@ -236,8 +240,6 @@ THIRD_PARTY_LIBS = []
 def library_recipes():
     result = []
 
-    LT_10_5 = bool(getDeptargetTuple() < (10, 5))
-
     # Since Apple removed the header files for the deprecated system
     # OpenSSL as of the Xcode 7 release (for OS X 10.10+), we do not
     # have much choice but to build our own copy here, too.
@@ -367,7 +369,7 @@ def library_recipes():
                             '-DSQLITE_ENABLE_RTREE '
                             '-DSQLITE_OMIT_AUTOINIT '
                             '-DSQLITE_TCL=0 '
-                 '%s' % ('','-DSQLITE_WITHOUT_ZONEMALLOC ')[LT_10_5]),
+                            ),
               configure_pre=[
                   '--enable-threadsafe',
                   '--enable-shared=no',
@@ -378,47 +380,6 @@ def library_recipes():
           ),
         ])
 
-    if getDeptargetTuple() < (10, 5):
-        result.extend([
-          dict(
-              name="Bzip2 1.0.6",
-              url="http://bzip.org/1.0.6/bzip2-1.0.6.tar.gz",
-              checksum='00b516f4704d4a7cb50a1d97e6e8e15b',
-              configure=None,
-              install='make install CC=%s CXX=%s, PREFIX=%s/usr/local/ CFLAGS="-arch %s"'%(
-                  CC, CXX,
-                  shellQuote(os.path.join(WORKDIR, 'libraries')),
-                  ' -arch '.join(ARCHLIST),
-              ),
-          ),
-          dict(
-              name="ZLib 1.2.3",
-              url="http://www.gzip.org/zlib/zlib-1.2.3.tar.gz",
-              checksum='debc62758716a169df9f62e6ab2bc634',
-              configure=None,
-              install='make install CC=%s CXX=%s, prefix=%s/usr/local/ CFLAGS="-arch %s"'%(
-                  CC, CXX,
-                  shellQuote(os.path.join(WORKDIR, 'libraries')),
-                  ' -arch '.join(ARCHLIST),
-              ),
-          ),
-          dict(
-              # Note that GNU readline is GPL'd software
-              name="GNU Readline 6.1.2",
-              url="http://ftp.gnu.org/pub/gnu/readline/readline-6.1.tar.gz" ,
-              checksum='fc2f7e714fe792db1ce6ddc4c9fb4ef3',
-              patchlevel='0',
-              patches=[
-                  # The readline maintainers don't do actual micro releases, but
-                  # just ship a set of patches.
-                  ('http://ftp.gnu.org/pub/gnu/readline/readline-6.1-patches/readline61-001',
-                   'c642f2e84d820884b0bf9fd176bc6c3f'),
-                  ('http://ftp.gnu.org/pub/gnu/readline/readline-6.1-patches/readline61-002',
-                   '1a76781a1ea734e831588285db7ec9b1'),
-              ]
-          ),
-        ])
-
     if not PYTHON_3:
         result.extend([
           dict(