Apple: Introduce separate system name for iOS, tvOS, and watchOS

- Remove code signing requirements for non-macOS
- Do not set deployment target for non-macOS
- Build static library for compiler feature detection for non-macOS
- Use framework to run CompilerId tests for watchOS
- Port tests to new SDK handling
- Add new Apple cross-compiling section to toolchain documentation

Closes: #17870

11 files changed, 42 insertions, 1 deletions

diff --git a/Modules/Platform/Darwin-Initialize.cmake b/Modules/Platform/Darwin-Initialize.cmake
index 3db77aa..2d797f6 100644
--- a/Modules/Platform/Darwin-Initialize.cmake
+++ b/Modules/Platform/Darwin-Initialize.cmake
@@ -34,7 +34,7 @@ string(REGEX REPLACE "^([0-9]+\\.[0-9]+).*$" "\\1"
 # CMAKE_OSX_DEPLOYMENT_TARGET
 
 # Set cache variable - end user may change this during ccmake or cmake-gui configure.
-if(_CURRENT_OSX_VERSION VERSION_GREATER 10.3)
+if(CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND _CURRENT_OSX_VERSION VERSION_GREATER 10.3)
   set(CMAKE_OSX_DEPLOYMENT_TARGET "$ENV{MACOSX_DEPLOYMENT_TARGET}" CACHE STRING
     "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
 endif()
@@ -49,6 +49,12 @@ elseif(NOT "x$ENV{SDKROOT}" STREQUAL "x" AND
         (NOT "x$ENV{SDKROOT}" MATCHES "/" OR IS_DIRECTORY "$ENV{SDKROOT}"))
   # Use the value of SDKROOT from the environment.
   set(_CMAKE_OSX_SYSROOT_DEFAULT "$ENV{SDKROOT}")
+elseif(CMAKE_SYSTEM_NAME STREQUAL iOS)
+  set(_CMAKE_OSX_SYSROOT_DEFAULT "iphoneos")
+elseif(CMAKE_SYSTEM_NAME STREQUAL tvOS)
+  set(_CMAKE_OSX_SYSROOT_DEFAULT "appletvos")
+elseif(CMAKE_SYSTEM_NAME STREQUAL watchOS)
+  set(_CMAKE_OSX_SYSROOT_DEFAULT "watchos")
 elseif("${CMAKE_GENERATOR}" MATCHES Xcode
        OR CMAKE_OSX_DEPLOYMENT_TARGET
        OR CMAKE_OSX_ARCHITECTURES MATCHES "[^;]"
diff --git a/Modules/Platform/Darwin.cmake b/Modules/Platform/Darwin.cmake
index 727baa6..a73ffba 100644
--- a/Modules/Platform/Darwin.cmake
+++ b/Modules/Platform/Darwin.cmake
@@ -1,5 +1,13 @@
 set(APPLE 1)
 
+if(CMAKE_SYSTEM_NAME STREQUAL "iOS" OR CMAKE_SYSTEM_NAME STREQUAL "tvOS" OR CMAKE_SYSTEM_NAME STREQUAL "watchOS")
+  set(CMAKE_MACOSX_BUNDLE ON)
+
+  set(CMAKE_FIND_ROOT_PATH "${_CMAKE_OSX_SYSROOT_PATH}")
+  set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+  set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+endif()
+
 # Darwin versions:
 #   6.x == Mac OSX 10.2 (Jaguar)
 #   7.x == Mac OSX 10.3 (Panther)
diff --git a/Modules/Platform/iOS-Determine-CXX.cmake b/Modules/Platform/iOS-Determine-CXX.cmake
new file mode 100644
index 0000000..ac80fa6
--- /dev/null
+++ b/Modules/Platform/iOS-Determine-CXX.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin-Determine-CXX)
diff --git a/Modules/Platform/iOS-Initialize.cmake b/Modules/Platform/iOS-Initialize.cmake
new file mode 100644
index 0000000..41399a3
--- /dev/null
+++ b/Modules/Platform/iOS-Initialize.cmake
@@ -0,0 +1,7 @@
+include(Platform/Darwin-Initialize)
+
+if(NOT _CMAKE_OSX_SYSROOT_PATH MATCHES "/iPhone(OS|Simulator)")
+  message(FATAL_ERROR "${CMAKE_OSX_SYSROOT} is not an iOS SDK")
+endif()
+
+set(_CMAKE_FEATURE_DETECTION_TARGET_TYPE STATIC_LIBRARY)
diff --git a/Modules/Platform/iOS.cmake b/Modules/Platform/iOS.cmake
new file mode 100644
index 0000000..850ddc2
--- /dev/null
+++ b/Modules/Platform/iOS.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin)
diff --git a/Modules/Platform/tvOS-Determine-CXX.cmake b/Modules/Platform/tvOS-Determine-CXX.cmake
new file mode 100644
index 0000000..ac80fa6
--- /dev/null
+++ b/Modules/Platform/tvOS-Determine-CXX.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin-Determine-CXX)
diff --git a/Modules/Platform/tvOS-Initialize.cmake b/Modules/Platform/tvOS-Initialize.cmake
new file mode 100644
index 0000000..6834c80
--- /dev/null
+++ b/Modules/Platform/tvOS-Initialize.cmake
@@ -0,0 +1,7 @@
+include(Platform/Darwin-Initialize)
+
+if(NOT _CMAKE_OSX_SYSROOT_PATH MATCHES "/AppleTV(OS|Simulator)")
+  message(FATAL_ERROR "${CMAKE_OSX_SYSROOT} is not an tvOS SDK")
+endif()
+
+set(_CMAKE_FEATURE_DETECTION_TARGET_TYPE STATIC_LIBRARY)
diff --git a/Modules/Platform/tvOS.cmake b/Modules/Platform/tvOS.cmake
new file mode 100644
index 0000000..850ddc2
--- /dev/null
+++ b/Modules/Platform/tvOS.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin)
diff --git a/Modules/Platform/watchOS-Determine-CXX.cmake b/Modules/Platform/watchOS-Determine-CXX.cmake
new file mode 100644
index 0000000..ac80fa6
--- /dev/null
+++ b/Modules/Platform/watchOS-Determine-CXX.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin-Determine-CXX)
diff --git a/Modules/Platform/watchOS-Initialize.cmake b/Modules/Platform/watchOS-Initialize.cmake
new file mode 100644
index 0000000..2f396d3
--- /dev/null
+++ b/Modules/Platform/watchOS-Initialize.cmake
@@ -0,0 +1,7 @@
+include(Platform/Darwin-Initialize)
+
+if(NOT _CMAKE_OSX_SYSROOT_PATH MATCHES "/Watch(OS|Simulator)")
+  message(FATAL_ERROR "${CMAKE_OSX_SYSROOT} is not an watchOS SDK")
+endif()
+
+set(_CMAKE_FEATURE_DETECTION_TARGET_TYPE STATIC_LIBRARY)
diff --git a/Modules/Platform/watchOS.cmake b/Modules/Platform/watchOS.cmake
new file mode 100644
index 0000000..850ddc2
--- /dev/null
+++ b/Modules/Platform/watchOS.cmake
@@ -0,0 +1 @@
+include(Platform/Darwin)