Add support for macos-15 for CI

Make sure to use Xcode 16.2 which fixed a clang compiler bug which would
generate incorrect optimized code in the 8g8 feature.

Turn off macos-12 because that has now been removed by GitHub Actions.
We will need to find an alternative way to build official legacy binary
releases.

Also, update Perl version to 5.34 as macOS-15 doesn't come with 5.30
anymore. Perl 5.34 has been installed on macOS 13 and above. Should not
be a huge deal as Perl isn't commonly used for plugins.

Author: ychin

.github/workflows/ci-macvim.yaml

@@ -22,7 +22,7 @@ env:
 
   MAKE_BUILD_ARGS: LINK_AS_NEEDED=yes # In macOS we never over-specify link dependencies and we already check against external deps in smoketest. With LTO, linking takes a while, so we want to avoid using link.sh.
 
-  VERSIONER_PERL_VERSION: '5.30'  # macOS default Perl installation uses this to determine which one to use
+  VERSIONER_PERL_VERSION: '5.34'  # macOS default Perl installation uses this to determine which one to use
 
   vi_cv_path_python: /Library/Frameworks/Python.framework/Versions/2.7/bin/python
   vi_cv_path_python3: "%s/bin/python3"
@@ -53,27 +53,31 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          # Oldest version of Xcode supported on GitHub Action to test source code backwards compatibility
-          # This version of Xcode can run on macOS 11 where as 13.3 has to run on macOS 12.
-          - os: macos-12
-            xcode: '13.2.1'
-            extra: [vimtags, check-xcodeproj-compat]
-
-          # Older version of Xcode, and used to publish legacy builds (for macOS 10.9 - 10.12)
-          - os: macos-12
-            xcode: '14.0' # last version of Xcode that uses the macOS 12 SDK, which still supports deploying to macOS 10.9
-            publish: true
-            legacy: true
-            publish_postfix: '_10.9'
+#          # Oldest version of Xcode supported on GitHub Action to test source code backwards compatibility
+#          # This version of Xcode can run on macOS 11 where as 13.3 has to run on macOS 12.
+#          - os: macos-12
+#            xcode: '13.2.1'
+#            extra: [vimtags, check-xcodeproj-compat]
+#
+#          # Older version of Xcode, and used to publish legacy builds (for macOS 10.9 - 10.12)
+#          - os: macos-12
+#            xcode: '14.0' # last version of Xcode that uses the macOS 12 SDK, which still supports deploying to macOS 10.9
+#            publish: true
+#            legacy: true
+#            publish_postfix: '_10.9'
 
           - os: macos-13
             xcode: '15.2'
+            extra: [vimtags, check-xcodeproj-compat]
+
+          # Below runners use Apple Silicon.
+          - os: macos-14
+            xcode: '15.4'
             optimized: true
 
           # Most up to date OS and Xcode. Used to publish release for the main build.
-          # This runner uses Apple Silicon.
-          - os: macos-14
-            xcode: '15.2'
+          - os: macos-15
+            xcode: '16.2'
             publish: true
             optimized: true