workflows/premerge: Enable macos builds (#125176)

We still have buildkite for testing Linux and Windows, so we don't need
to enable those builds yet.

Author: tstellar

.github/workflows/premerge.yaml

@@ -5,16 +5,14 @@ permissions:
 
 on:
   pull_request:
-    paths:
-      - .github/workflows/premerge.yaml
   push:
     branches:
       - 'main'
       - 'release/**'
 
 jobs:
   premerge-checks-linux:
-    if: github.repository_owner == 'llvm'
+    if: false && github.repository_owner == 'llvm'
     runs-on: llvm-premerge-linux-runners
     concurrency:
       group: ${{ github.workflow }}-linux-${{ github.event.pull_request.number || github.sha }}
@@ -73,7 +71,7 @@ jobs:
           ./.ci/monolithic-linux.sh "$(echo ${linux_projects} | tr ' ' ';')" "$(echo ${linux_check_targets})" "$(echo ${linux_runtimes} | tr ' ' ';')" "$(echo ${linux_runtime_check_targets})"
 
   premerge-checks-windows:
-    if: github.repository_owner == 'llvm'
+    if: false && github.repository_owner == 'llvm'
     runs-on: llvm-premerge-windows-runners
     concurrency:
       group: ${{ github.workflow }}-windows-${{ github.event.pull_request.number || github.sha }}