ci(macos): route x86_64 builds to local self-hosted runner

GitHub-hosted macos-13 Intel runners have long queue times; a local
self-hosted runner with default labels [self-hosted, macOS, X64] is
used instead. arm64 and universal builds are unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ghirpara

.github/workflows/build-macos.yml

@@ -23,7 +23,7 @@ on:
 
 jobs:
   build:
-    runs-on: ${{ inputs.architecture == 'arm64' && 'macos-14' || 'macos-13' }}
+    runs-on: ${{ inputs.architecture == 'arm64' && 'macos-14' || inputs.architecture == 'x86_64' && fromJSON('["self-hosted", "macOS", "X64"]') || 'macos-13' }}
     outputs:
       artifact-name: ${{ steps.upload.outputs.artifact-name }}