ci: Clean up broken cobalt checkout in depot tools step (#8585)

Improve CI reliability by ensuring a clean state in the depot tools
setup
step. Previously, inconsistent submodule states could cause checkout
failures on runners. This change deinitializes all submodules and
performs
a deep clean of the cobalt source directory.

Bug: 407051026

Author: oxve

.github/actions/depot_tools/action.yaml

@@ -17,8 +17,13 @@ runs:
       - name: Clear Cache and Clone Depot Tools
         if: inputs.use_cache != 'true'
         run: |
+          set -x
+          # Remove and re-clone gclient.
           rm -rf /runner-cache/depot_tools /runner-cache/cobalt/.cipd_cache
           git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git /runner-cache/depot_tools
+
+          # Reset cobalt checkout by deleting all submodules and cleaning all non-tracked files.
+          git -C /runner-cache/cobalt/src submodule deinit -f --all
           git -C /runner-cache/cobalt/src clean -ffdx
         shell: bash
 

.github/workflows/main.yaml

@@ -340,8 +340,6 @@ jobs:
 
       - name: Checkout
         uses: actions/checkout@v4
-        # TODO(bug?): android debug builds are broken.
-        if: ${{ ! (contains(matrix.platform, 'android') && matrix.config == 'debug') }}
         with:
           path: cobalt/src
           # Set fetch-depth to 2 to make checkout faster for pull requests and cobalt_sandbox repo.
@@ -452,8 +450,10 @@ jobs:
         include: ${{ fromJson(needs.initialize.outputs.includes) }}
         config: [devel]
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - name: Restore CI Essentials
+        uses: actions/download-artifact@v4
+        with:
+          name: ci-essentials-${{ inputs.platform }}
       - name: Run E2E Tests
         uses: ./.github/actions/internal_tests
         with:
@@ -482,8 +482,10 @@ jobs:
         include: ${{ fromJson(needs.initialize.outputs.includes) }}
         config: [devel]
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - name: Restore CI Essentials
+        uses: actions/download-artifact@v4
+        with:
+          name: ci-essentials-${{ inputs.platform }}
       - name: Run YTS Tests
         uses: ./.github/actions/internal_tests
         with: