Add linux-64x11 as linux's elf loader. (#2763)

This forces linux to build the loader_app_install,
elf_loader_sandbox_install, and native_target/crashpad_handler targets.

b/323963204

.github/config/linux.json

@@ -1,5 +1,6 @@
 {
   "docker_service": "build-linux",
+  "bootloader": "linux-x64x11",
   "on_host_test": true,
   "on_host_test_shards": ["0", "1", "2", "3", "blackbox", "wpt"],
   "platforms": [

.github/workflows/main.yaml

@@ -277,10 +277,10 @@ jobs:
            echo "COBALT_BOOTLOADER=${COBALT_BOOTLOADER}" >> $GITHUB_ENV
       # Build bootloader for on-host tests if necessary.
       - name: Bootloader GN
-        if: ${{ needs.initialize.outputs.bootloader != 'null' && matrix.config == 'devel' }}
+        if: ${{ needs.initialize.outputs.bootloader != 'null' && ( matrix.config == 'devel' || matrix.config == 'qa' ) }}
         uses: ./.github/actions/gn
       - name: Build Bootloader
-        if: ${{ needs.initialize.outputs.bootloader != 'null' && matrix.config == 'devel' }}
+        if: ${{ needs.initialize.outputs.bootloader != 'null' && ( matrix.config == 'devel' || matrix.config == 'qa' ) }}
         uses: ./.github/actions/build
       - name: Upload Bootloader On Host Test Artifacts
         if: ${{ needs.initialize.outputs.bootloader != 'null' && matrix.config == 'devel' && needs.initialize.outputs.on_host_test == 'true'}}