Revert ExternalProject and FetchContent refactoring

Refactoring of the ExternalProject and FetchContent modules moved
the commands into CMake scripts. This broke custom commands that
used shell redirection or special build tool variables of the form
$(MakeVar). Undo the sequence of commits that performed this
refactoring and follow-up fixes associated with it.

The following commits are reverted by this change:

4f3d1abbb4 (ExternalProject: Refactor pre-configure steps to support
no-target uses, 2021-02-05)

17e5516e60 (FetchContent: Invoke steps directly and avoid a separate
sub-build, 2021-01-29)

bd876f3849 (FetchContent: Restore patch command support,
2021-02-18)

404cddb7bb (ExternalProject: Fix misuse of IS_NEWER_THAN in
timestamp checks, 2021-02-21)

b0da671243 (FetchContent: Don't update timestamps if files don't
change, 2021-02-18)

Fixes: #21892

1 files changed, 173 insertions, 0 deletions

diff --git a/Modules/ExternalProject-download.cmake.in b/Modules/ExternalProject-download.cmake.in
new file mode 100644
index 0000000..ff8c659
--- /dev/null
+++ b/Modules/ExternalProject-download.cmake.in
@@ -0,0 +1,173 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+cmake_minimum_required(VERSION 3.5)
+
+function(check_file_hash has_hash hash_is_good)
+  if("${has_hash}" STREQUAL "")
+    message(FATAL_ERROR "has_hash Can't be empty")
+  endif()
+
+  if("${hash_is_good}" STREQUAL "")
+    message(FATAL_ERROR "hash_is_good Can't be empty")
+  endif()
+
+  if("@ALGO@" STREQUAL "")
+    # No check
+    set("${has_hash}" FALSE PARENT_SCOPE)
+    set("${hash_is_good}" FALSE PARENT_SCOPE)
+    return()
+  endif()
+
+  set("${has_hash}" TRUE PARENT_SCOPE)
+
+  message(STATUS "verifying file...
+       file='@LOCAL@'")
+
+  file("@ALGO@" "@LOCAL@" actual_value)
+
+  if(NOT "${actual_value}" STREQUAL "@EXPECT_VALUE@")
+    set("${hash_is_good}" FALSE PARENT_SCOPE)
+    message(STATUS "@ALGO@ hash of
+    @LOCAL@
+  does not match expected value
+    expected: '@EXPECT_VALUE@'
+      actual: '${actual_value}'")
+  else()
+    set("${hash_is_good}" TRUE PARENT_SCOPE)
+  endif()
+endfunction()
+
+function(sleep_before_download attempt)
+  if(attempt EQUAL 0)
+    return()
+  endif()
+
+  if(attempt EQUAL 1)
+    message(STATUS "Retrying...")
+    return()
+  endif()
+
+  set(sleep_seconds 0)
+
+  if(attempt EQUAL 2)
+    set(sleep_seconds 5)
+  elseif(attempt EQUAL 3)
+    set(sleep_seconds 5)
+  elseif(attempt EQUAL 4)
+    set(sleep_seconds 15)
+  elseif(attempt EQUAL 5)
+    set(sleep_seconds 60)
+  elseif(attempt EQUAL 6)
+    set(sleep_seconds 90)
+  elseif(attempt EQUAL 7)
+    set(sleep_seconds 300)
+  else()
+    set(sleep_seconds 1200)
+  endif()
+
+  message(STATUS "Retry after ${sleep_seconds} seconds (attempt #${attempt}) ...")
+
+  execute_process(COMMAND "${CMAKE_COMMAND}" -E sleep "${sleep_seconds}")
+endfunction()
+
+if("@LOCAL@" STREQUAL "")
+  message(FATAL_ERROR "LOCAL can't be empty")
+endif()
+
+if("@REMOTE@" STREQUAL "")
+  message(FATAL_ERROR "REMOTE can't be empty")
+endif()
+
+if(EXISTS "@LOCAL@")
+  check_file_hash(has_hash hash_is_good)
+  if(has_hash)
+    if(hash_is_good)
+      message(STATUS "File already exists and hash match (skip download):
+  file='@LOCAL@'
+  @ALGO@='@EXPECT_VALUE@'"
+      )
+      return()
+    else()
+      message(STATUS "File already exists but hash mismatch. Removing...")
+      file(REMOVE "@LOCAL@")
+    endif()
+  else()
+    message(STATUS "File already exists but no hash specified (use URL_HASH):
+  file='@LOCAL@'
+Old file will be removed and new file downloaded from URL."
+    )
+    file(REMOVE "@LOCAL@")
+  endif()
+endif()
+
+set(retry_number 5)
+
+message(STATUS "Downloading...
+   dst='@LOCAL@'
+   timeout='@TIMEOUT_MSG@'
+   inactivity timeout='@INACTIVITY_TIMEOUT_MSG@'"
+)
+set(download_retry_codes 7 6 8 15)
+set(skip_url_list)
+set(status_code)
+foreach(i RANGE ${retry_number})
+  if(status_code IN_LIST download_retry_codes)
+    sleep_before_download(${i})
+  endif()
+  foreach(url @REMOTE@)
+    if(NOT url IN_LIST skip_url_list)
+      message(STATUS "Using src='${url}'")
+
+      @TLS_VERIFY_CODE@
+      @TLS_CAINFO_CODE@
+      @NETRC_CODE@
+      @NETRC_FILE_CODE@
+
+      file(
+        DOWNLOAD
+        "${url}" "@LOCAL@"
+        @SHOW_PROGRESS@
+        @TIMEOUT_ARGS@
+        @INACTIVITY_TIMEOUT_ARGS@
+        STATUS status
+        LOG log
+        @USERPWD_ARGS@
+        @HTTP_HEADERS_ARGS@
+        )
+
+      list(GET status 0 status_code)
+      list(GET status 1 status_string)
+
+      if(status_code EQUAL 0)
+        check_file_hash(has_hash hash_is_good)
+        if(has_hash AND NOT hash_is_good)
+          message(STATUS "Hash mismatch, removing...")
+          file(REMOVE "@LOCAL@")
+        else()
+          message(STATUS "Downloading... done")
+          return()
+        endif()
+      else()
+        string(APPEND logFailedURLs "error: downloading '${url}' failed
+        status_code: ${status_code}
+        status_string: ${status_string}
+        log:
+        --- LOG BEGIN ---
+        ${log}
+        --- LOG END ---
+        "
+        )
+      if(NOT status_code IN_LIST download_retry_codes)
+        list(APPEND skip_url_list "${url}")
+        break()
+      endif()
+    endif()
+  endif()
+  endforeach()
+endforeach()
+
+message(FATAL_ERROR "Each download failed!
+  ${logFailedURLs}
+  "
+)