GitHub Actions: add the macos-11 virtual environment.

Reference: https://github.com/actions/virtual-environments

Author: leleliu008

.github/workflows/cross-compile-android-ndk.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build-machine-os: [ubuntu-18.04, ubuntu-20.04, macos-10.15]
+        build-machine-os: [ubuntu-18.04, ubuntu-20.04, macos-10.15, macos-11]
 
     runs-on: ${{ matrix.build-machine-os }}
 

.github/workflows/cross-compile-mingw-w64.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build-machine-os: [ubuntu-18.04, ubuntu-20.04, macos-10.15]
+        build-machine-os: [ubuntu-18.04, ubuntu-20.04, macos-10.15, macos-11]
         target: [i686-w64-mingw32,x86_64-w64-mingw32]
 
     runs-on: ${{ matrix.build-machine-os }}

.github/workflows/testing-mac.yml

@@ -11,8 +11,7 @@ jobs:
 
     strategy:
       matrix:
-        # os: [macos-11.0, macos-10.15]
-        os: [macos-10.15]
+        os: [macos-11, macos-10.15]
         compiler: [gcc, clang]
 
     runs-on: ${{ matrix.os }}