setup.sh: install pinned llvm@19/lld@19 Intel bottles from a local tap

Co-authored-by: Xmader <16057139+Xmader@users.noreply.github.com>

Author: Copilot

setup.sh

@@ -28,11 +28,25 @@ elif [[ "$OSTYPE" == "darwin"* ]]; then # macOS
   # `llvm`/`lld` have no bottles for Intel macOS or macOS 14 and build from
   # source for hours (and lld pulls in the unversioned llvm). Both kegs are
   # keg-only, so put them on PATH explicitly.
+  USE_MOZ_BOOTSTRAP_CLANG=0
   if [[ "$(uname -m)" == "x86_64" ]]; then
-    # Homebrew no longer ships llvm@19/lld@19 bottles for Intel macOS and would
-    # build LLVM from source (which fails), so use the clang toolchain that
-    # Mozilla's own bootstrap downloads once the source is extracted (below).
-    echo "Intel macOS: will use Mozilla's bootstrapped clang"
+    # Homebrew's current llvm@19/lld@19 formulae have no Intel bottles, so brew
+    # would build LLVM from source (hours, then fails). Install the last
+    # formula revisions that still listed the Intel (`sonoma`) bottles from a
+    # local tap instead; those are `cellar: :any` so they run on newer macOS.
+    HB_PIN=2a2d17bc2f926b69105a1ca221761d39e65bf737 # homebrew-core commit
+    brew tap-new --no-git local/pythonmonkey >/dev/null
+    HB_TAP="$(brew --repository local/pythonmonkey)/Formula"
+    mkdir -p "$HB_TAP"
+    for f in 'llvm@19' 'lld@19'; do
+      curl -fsSL -o "$HB_TAP/$f.rb" "https://raw.githubusercontent.com/Homebrew/homebrew-core/$HB_PIN/Formula/${f:0:1}/$f.rb"
+    done
+    if HOMEBREW_DEVELOPER=1 brew install --force-bottle local/pythonmonkey/llvm@19 local/pythonmonkey/lld@19; then
+      export PATH="$(brew --prefix llvm@19)/bin:$(brew --prefix lld@19)/bin:$PATH"
+    else
+      echo "Pinned Intel bottles unavailable; falling back to Mozilla's bootstrapped clang"
+      USE_MOZ_BOOTSTRAP_CLANG=1
+    fi
   else
     brew install llvm@19 lld@19
     export PATH="$(brew --prefix llvm@19)/bin:$(brew --prefix lld@19)/bin:$PATH"
@@ -94,7 +108,7 @@ echo "Done downloading spidermonkey source code"
 echo "Building spidermonkey"
 cd firefox-source
 
-if [[ "$OSTYPE" == "darwin"* && "$(uname -m)" == "x86_64" ]]; then
+if [[ "${USE_MOZ_BOOTSTRAP_CLANG:-0}" == 1 ]]; then
   # Fetch Mozilla's prebuilt clang (>= 19) for Intel macOS, see above
   python3 ./mach --no-interactive bootstrap --application-choice=js --no-system-changes
   export PATH="$HOME/.mozbuild/clang/bin:$PATH"