Temporarily use fastbuild for OS X workerd release builds

The root cause of bus errors from workerd opt builds are being
investigated. In the interim, use fastbuild instead.

The impact of this workaround is that the uncompressed macOS arm64
binary goes from 61MB to 155MB. The compressed binary increases from
21MB to 35MB.

Bug: cloudflare/workers-sdk#2386
Bug: CUSTESC-29094

build-releases.sh

@@ -15,9 +15,12 @@ TAG_NAME=$(curl -sL https://api.github.com/repos/cloudflare/workerd/releases/lat
 git checkout $TAG_NAME
 
 # Build macOS binary
-pnpm exec bazelisk build --disk_cache=./.bazel-cache -c opt //src/workerd/server:workerd
-
-cp bazel-bin/src/workerd/server/workerd ./workerd-darwin-arm64
+#
+# This is using fastbuild rather than opt until SIGBUS issue with the opt binary are resolved.
+# The issue is tracked in https://github.com/cloudflare/workers-sdk/issues/2386.
+pnpm exec bazelisk build -c fastbuild //src/workerd/server:workerd
+echo Stripping binary
+strip bazel-bin/src/workerd/server/workerd -o ./workerd-darwin-arm64
 
 docker buildx build --platform linux/arm64 -f Dockerfile.release -t workerd:$TAG_NAME --target=artifact --output type=local,dest=$(pwd) .