add linux-aarch64 build

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitlab-ci.yml

@@ -42,6 +42,10 @@ include:
   - project: 'libretro-infrastructure/ci-templates'
     file: '/linux-i686.yml'
 
+  # Linux 64-bit (ARM)
+  - project: 'libretro-infrastructure/ci-templates'
+    file: '/linux-aarch64.yml'
+
   # MacOS 64-bit
   - project: 'libretro-infrastructure/ci-templates'
     file: '/osx-x64.yml'
@@ -170,6 +174,12 @@ libretro-build-linux-i686:
     - .libretro-linux-i686-make-default
     - .core-defs
 
+# Linux 64-bit (ARM)
+libretro-build-linux-aarch64:
+  extends:
+    - .libretro-linux-aarch64-make-default
+    - .core-defs
+
 # MacOS 64-bit
 libretro-build-osx-x64:
   extends: