fix(action): update variant matrix handling for improved flexibility in workflows

Co-authored-by: Copilot <copilot@github.com>

.github/workflows/build.yml

@@ -31,10 +31,10 @@ on:
 jobs:
   build-gki:
     name: "${{ inputs.kernel_version }} (${{ matrix.variant }})"
-    strategy:
-      fail-fast: false
-      matrix:
-        variant: ${{ inputs.variant == 'All' && fromJson('["Normal","Bypass","Wild"]') || fromJson('["' ~ inputs.variant ~ '"]') }}
+      strategy:
+        fail-fast: false
+        matrix:
+          variant: ${{ (inputs.variant == 'All' && 'Normal,Bypass,Wild' || inputs.variant) .split(',') }}
     runs-on: ubuntu-latest
     timeout-minutes: 60