.github: rely on new llvm-project checkout

This is now baked into the docker images to speed up
premerge cycle times.

Author: gburgessiv

.github/workflows/premerge.yaml

@@ -26,6 +26,11 @@ concurrency:
 jobs:
   premerge-checks-linux:
     name: Linux Premerge Checks (Test Only - Please Ignore Results)
+    defaults:
+      run:
+        # The premerge Linux docker instance keeps a pristine clone of LLVM in
+        # /home/gha/llvm-project; that should be used as our main workdir.
+        working-directory: /home/gha/llvm-project
     if: >-
         github.repository_owner == 'llvm' &&
         (github.event_name != 'pull_request' || github.event.action != 'closed')
@@ -34,7 +39,7 @@ jobs:
       - name: Checkout LLVM
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          fetch-depth: 2
+          path: /home/gha/llvm-project
       - name: Setup ccache
         uses: hendrikmuhs/ccache-action@a1209f81afb8c005c13b4296c32e363431bffea5 # v1.2.17
         with: