Use different cache keys for different macOS builds

.gitlab-ci.yml

@@ -115,7 +115,7 @@ Debian_Clang_tests:
     CCACHE_SIZE: 1G
     BUILD_TESTS_ONLY: 1
 
-MacOS:
+.MacOS:
   image: macos-11-xcode-12
   tags:
     - macos
@@ -123,8 +123,14 @@ MacOS:
   only:
     variables:
       - $CI_PROJECT_ID == "7107382"
+  cache:
+    paths:
+    - ccache/
   script:
     - rm -fr build/*  # remove anything in the build directory
+    - export CCACHE_BASEDIR="$(pwd)"
+    - export CCACHE_DIR="$(pwd)/ccache"
+    - mkdir -pv "${CCACHE_DIR}"
     - CI/before_install.osx.sh
     - CI/before_script.osx.sh
     - cd build; make -j $(sysctl -n hw.logicalcpu) package
@@ -134,9 +140,17 @@ MacOS:
       - build/OpenMW-*.dmg
       - "build/**/*.log"
 
+macOS11_Xcode12:
+  extends: .MacOS
+  image: macos-11-xcode-12
+  cache:
+    key: macOS11_Xcode12.v1
+
 macOS10.15_Xcode11:
-  extends: MacOS
+  extends: .MacOS
   image: macos-10.15-xcode-11
+  cache:
+    key: macOS10.15_Xcode11.v1
 
 variables: &engine-targets
   targets: "openmw,openmw-essimporter,openmw-iniimporter,openmw-launcher,openmw-wizard"