Adding yamato script to crossbuild apple silicon support.

Trying my shiny new mac image with latest OS and xcode

.yamato/build_osx_arm64.yml

@@ -0,0 +1,33 @@
+{% metadata_file .yamato/Globals.metafile %}
+---
+name: Build OSX ARM64
+
+agent:
+  type: Unity::VM::osx
+  image: platform-foundation/mac-10.15-bokken:latest
+  flavor: m1.mac
+
+variables:
+  ARTIFACT_FILENAME: {{globals.artifact_base_name}}-osx-arm64.7z
+
+commands:
+  - mkdir artifacts
+  - curl https://public-stevedore.unity3d.com/r/public/7za-mac-x64/e6c75fb7ffda_5bd76652986a0e3756d1cfd7e84ce056a9e1dbfc5f70f0514a001f724c0fbad2.zip --output artifacts/7za-mac-x64.zip
+  - unzip artifacts/7za-mac-x64.zip -d artifacts/7za-mac-x64
+  - |
+    cd unity/unitygc
+    mkdir release
+    cd release
+    cmake -DCMAKE_OSX_ARCHITECTURES=arm64 -DCMAKE_BUILD_TYPE=Release ..
+    cmake --build .
+  - LD_LIBRARY_PATH=/usr/local/opt/openssl/lib ./build.sh -subset clr+libs -a arm64 -c release -cross -ci -ninja /p:CrossBuild=true
+  - cp unity/unitygc/release/libunitygc.dylib artifacts/bin/microsoft.netcore.app.runtime.osx-arm64/Release/runtimes/osx-arm64/native
+  - artifacts/7za-mac-x64/7za a artifacts/unity/$ARTIFACT_FILENAME ./artifacts/bin/microsoft.netcore.app.runtime.osx-arm64/Release/runtimes/osx-arm64
+
+artifacts:
+  osx-arm64-7z:
+    paths:
+      - artifacts/unity/**
+  osx-arm64:
+    paths:
+      - artifacts/bin/**

.yamato/test_osx_arm64.yml

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+{% metadata_file .yamato/Globals.metafile %}
+---
+name: Test OSX ARM64
+
+agent:
+  type: Unity::VM::osx
+  image: platform-foundation/mac-bokken:v0.1.8-972754
+  flavor: m1.mac
+
+dependencies:
+  - path: .yamato/build_osx_arm64.yml
+
+commands:
+# build/run tests
+  - dotnet build unity/managed.sln -c Release
+  - |
+    cd unity/embed_api_tests
+    cmake -DCMAKE_BUILD_TYPE=Release .
+    cmake --build .
+    ./mono_test_app
+  - LD_LIBRARY_PATH=/usr/local/opt/openssl/lib ./build.sh -subset libs.tests -test -a arm64 -c release -ci -ninja
+  - ./src/tests/build.sh arm64 release ci
+  - ./src/tests/run.sh arm64 release
+  - ./build.sh clr.paltests
+  - ./artifacts/bin/coreclr/OSX.arm64.Debug/paltests/runpaltests.sh $(pwd)/artifacts/bin/coreclr/OSX.arm64.Debug/paltests
+
+triggers:
+  pull_requests:
+    - targets:
+        only:
+          - "unity-main"