TOOLS/macos-sdk-version: remove legacy sdk version retrieval

older macOS dev tools were inconsistent with the way how SDK versions
were returned, some truncated the minor versions. in those cases the
SDK version had to be retrieved through the SDK build version.

recently the scheme for the SDK build version changed that our heuristic
for converting it to an SDK version produced wrong version strings.
the stride of the minor version changed from 1 to 2, so SDK versions
ended up higher than they actually were. furthermore macOS 11 was
hardcoded.

since Xcode 12 Apple fixed the SDK version retrieval and it is no longer
truncated when using Xcode as dev tools. Xcode 12 is also the latest
supported version on macOS 10.15, which is also our oldest supported
version. we can remove the old SDK build version conversation and use
the Xcode only tool to retrieve the SDK version in the case Xcode is
used as dev tools. furthermore this als keeps support for Xcode 11 where
the problem wasn't fixed yet, but is still a supported version on macOS
10.15.

Fixes #9907

TOOLS/macos-sdk-version.py

@@ -6,6 +6,7 @@
 import re
 import os
 import string
+import subprocess
 import sys
 from shutil import which
 from subprocess import check_output
@@ -13,11 +14,11 @@ from subprocess import check_output
 def find_macos_sdk():
     sdk = os.environ.get('MACOS_SDK', '')
     sdk_version = os.environ.get('MACOS_SDK_VERSION', '0.0')
-    build_version = '0.0'
     xcrun = which('xcrun')
+    xcodebuild = which('xcodebuild')
 
     if not xcrun:
-        return sdk,sdk_version,build_version
+        return sdk,sdk_version
 
     if not sdk:
         sdk = check_output([xcrun, '--sdk', 'macosx', '--show-sdk-path'],
@@ -25,36 +26,20 @@ def find_macos_sdk():
 
     # find macOS SDK paths and version
     if sdk_version == '0.0':
-        # show-sdk-build-version: is not available on older command line tools, but returns a build version (eg 17A360)
-        # show-sdk-version: is always available, but on older dev tools it's only the major version
-        sdk_build_version = check_output([xcrun, '--sdk', 'macosx',
-                                          '--show-sdk-build-version'], encoding="UTF-8")
-
         sdk_version = check_output([xcrun, '--sdk', 'macosx', '--show-sdk-version'],
                                     encoding="UTF-8")
 
-    if sdk:
-        build_version = '10.10.0'
-
-    # convert build version to a version string
-    # first 2 two digits are the major version, starting with 15 which is 10.11 (offset of 4)
-    # 1 char is the minor version, A => 0, B => 1 and ongoing
-    # last digits are bugfix version, which are not relevant for us
-    # eg 16E185 => 10.12.4, 17A360 => 10.13, 18B71 => 10.14.1
-    if sdk_build_version and isinstance(sdk_build_version, str):
-        verRe = re.compile("(\d+)(\D+)(\d+)")
-        version_parts = verRe.search(sdk_build_version)
-        major = int(version_parts.group(1)) - 4
-        minor = string.ascii_lowercase.index(version_parts.group(2).lower())
-        build_version = '10.' + str(major) + '.' + str(minor)
-        # from 20 onwards macOS 11.0 starts
-        if int(version_parts.group(1)) >= 20:
-            build_version = '11.' + str(minor)
+        # use xcode tools when installed, still necessary for xcode versions <12.0
+        try:
+            sdk_version = check_output([xcodebuild, '-sdk', 'macosx', '-version', 'ProductVersion'],
+                                        encoding="UTF-8", stderr=subprocess.DEVNULL)
+        except:
+            pass
 
     if not isinstance(sdk_version, str):
         sdk_version = '10.10.0'
 
-    return sdk,sdk_version,build_version
+    return sdk.strip(),sdk_version.strip()
 
 if __name__ == "__main__":
     sdk_info = find_macos_sdk()

meson.build

@@ -1464,10 +1464,8 @@ macos_sdk_path = ''
 macos_sdk_version = '0.0'
 if darwin and macos_sdk_version_py.found()
     macos_sdk_info = run_command(macos_sdk_version_py, check: true).stdout().split(',')
-    macos_sdk_path = macos_sdk_info[0].strip()
-    # Always pick whichever version is higher.
-    macos_sdk_version = macos_sdk_info[1].version_compare('>' + macos_sdk_info[2]) ? \
-                        macos_sdk_info[1] : macos_sdk_info[2]
+    macos_sdk_path = macos_sdk_info[0]
+    macos_sdk_version = macos_sdk_info[1]
 endif
 
 if macos_sdk_path != ''