Upgrade to Xcode 15, avoid duplicate unwind info on x86 macOS

.bazelrc

@@ -144,6 +144,13 @@ build:macos --config=unix
 # TODO (cleanup): macOS 11.X is now EOL, bump this to macOS 12.5 soon.
 build:macos --macos_minimum_os=11.5 --host_macos_minimum_os=11.5
 
+# Avoid emitting duplicate unwind info where compact unwind info can be used. This reduces the
+# object size by ~5% on average, improving disk space usage and link times. The final binary size
+# is not affected. Note that this is on-by-default on arm64, but turning it on for all mac builds
+# is easier than adding the flag only on x86. See https://reviews.llvm.org/D122258 for detailed
+# information on the flag.
+build:macos --copt='-femit-dwarf-unwind=no-compact-unwind'
+
 # On Linux, always link libc++ statically to avoid compatibility issues with different OS versions.
 # macOS links with dynamic libc++ by default, which has good backwards compatibility.
 build:linux --cxxopt='-stdlib=libc++' --host_cxxopt='-stdlib=libc++'

.github/workflows/release.yml

@@ -89,7 +89,7 @@ jobs:
       - name: Setup macOS
         if: runner.os == 'macOS'
         run: |
-          sudo xcode-select -s "/Applications/Xcode_14.3.1.app"
+          sudo xcode-select -s "/Applications/Xcode_15.1.app"
       - name: Setup Windows
         if: runner.os == 'Windows'
         run: |

.github/workflows/test.yml

@@ -60,6 +60,8 @@ jobs:
         # libc++, but this appears to cause errors so they are also being explicitly installed.
         # Since the GitHub runner image comes with a number of preinstalled packages, we don't need
         # to use APT much otherwise.
+        # TODO(cleanup): Upgrade this to LLVM 16 as soon as it is available on the latest Ubuntu
+        # LTS release. Debian includes LLVM 16 since the Bookworm 12.4 point release.
         run: |
           export DEBIAN_FRONTEND=noninteractive
           wget https://apt.llvm.org/llvm.sh
@@ -71,16 +73,16 @@ jobs:
           sed -i -e "s%llvm-symbolizer%/usr/lib/llvm-15/bin/llvm-symbolizer%" .bazelrc
       - name: Setup macOS
         if: matrix.os.name == 'macOS'
-        # TODO: We want to symbolize stacks for crashes on CI. Xcode is currently based on LLVM 15
+        # TODO: We want to symbolize stacks for crashes on CI. Xcode is currently based on LLVM 16
         # and the macos-13 image has llvm@15 installed:
         # https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md
         #
         # Not enabled because symbolication does not work on workerd macOS builds yet and running
         # llvm-symbolizer in the currently broken state causes some tests to time out on the
         # runner.
-        # Use Xcode 14.3.1 for now, upgrade once 15.1 is available on the runner image.
+        # Use latest available Xcode version – runner still defaults to 14.3.1.
         run: |
-          sudo xcode-select -s "/Applications/Xcode_14.3.1.app"
+          sudo xcode-select -s "/Applications/Xcode_15.1.app"
           # export LLVM_SYMBOLIZER=$(brew --prefix llvm@15)/bin/llvm-symbolizer
           # sed -i -e "s%llvm-symbolizer%${LLVM_SYMBOLIZER}%" .bazelrc
       - name: Setup Windows

README.md

@@ -78,7 +78,7 @@ To build `workerd`, you need:
   * LLD 15+ (e.g. package `lld-15`).
   * `python3`, `python3-distutils`, and `tcl8.6`
 * On macOS:
-  * Xcode 14.3+ installation (available on macOS 13 and higher)
+  * Xcode 15 installation (available on macOS 13 and higher)
   * Homebrew installed `tcl-tk` package (provides Tcl 8.6)
 * On Windows:
   * Install [App Installer](https://learn.microsoft.com/en-us/windows/package-manager/winget/#install-winget)