CI: Use arch variable in ci.yml instead of always using 'Lagom'

This was a relic from the SerenityOS CI, where architecture meant
what architecture to build Serenity for. For just ladybird, we might
want to build ladybird for multiple architectures per OS.

.github/workflows/ci.yml

@@ -16,6 +16,7 @@ jobs:
       matrix:
         os_name: ['Linux']
         os: [ubuntu-24.04]
+        arch: ['x86_64']
         fuzzer: ['NO_FUZZ']
         toolchain: ['GNU']
         clang_plugins: [false]
@@ -23,18 +24,21 @@ jobs:
         include:
           - os_name: 'Linux'
             os: ubuntu-24.04
+            arch: 'x86_64'
             fuzzer: 'NO_FUZZ'
             toolchain: 'Clang'
             clang_plugins: true
 
           - os_name: 'macOS'
             os: macos-15
+            arch: 'arm64'
             fuzzer: 'NO_FUZZ'
             toolchain: 'Clang'
             clang_plugins: false
 
           - os_name: 'Linux'
             os: ubuntu-24.04
+            arch: 'x86_64'
             fuzzer: 'FUZZ'
             toolchain: 'Clang'
             clang_plugins: false
@@ -44,5 +48,6 @@ jobs:
       toolchain: ${{ matrix.toolchain }}
       os_name: ${{ matrix.os_name }}
       os: ${{ matrix.os }}
+      arch: ${{ matrix.arch }}
       fuzzer: ${{ matrix.fuzzer }}
       clang_plugins: ${{ matrix.clang_plugins }}

.github/workflows/lagom-template.yml

@@ -12,6 +12,9 @@ on:
         os:
           required: true
           type: string
+        arch:
+          required: true
+          type: string
         fuzzer:
           required: false
           type: string
@@ -55,7 +58,7 @@ jobs:
         uses: ./.github/actions/setup
         with:
           os: ${{ inputs.os_name }}
-          arch: 'Lagom'
+          arch: ${{ inputs.arch }}
 
       # === PREPARE FOR BUILDING ===
 
@@ -88,7 +91,7 @@ jobs:
         id: 'cache-restore'
         with:
           os: ${{ inputs.os_name }}
-          arch: 'Lagom'
+          arch: ${{ inputs.arch }}
           toolchain: ${{ inputs.toolchain }}
           cache_key_extra: ${{ steps.build-parameters.outputs.ccache_key }}
           ccache_path: ${{ env.CCACHE_DIR }}
@@ -173,7 +176,7 @@ jobs:
       - name: Save Caches
         uses: ./.github/actions/cache-save
         with:
-          arch: 'Lagom'
+          arch: ${{ inputs.arch }}
           ccache_path: ${{ env.CCACHE_DIR }}
           ccache_primary_key: ${{ steps.cache-restore.outputs.ccache_primary_key }}