Optimise CI with faster Linux machines (#923)

* Optimise CI with faster machines

Build on 16 vCPU machine instead of the default 4 vCPU, using GitHub Action's beta of GitHub-hosted larger runner.

* Use Windows runner

* Remove windows custom runner

Author: repi

.github/workflows/ci.yaml

@@ -12,13 +12,13 @@ jobs:
     strategy:
       matrix:
         include:
-          - os: ubuntu-20.04
+          - os: ubuntu-20.04-16core
             target: x86_64-unknown-linux-gnu
           - os: windows-latest
             target: x86_64-pc-windows-msvc
           - os: macOS-latest
             target: x86_64-apple-darwin
-          - os: ubuntu-20.04
+          - os: ubuntu-20.04-16core
             target: aarch64-linux-android
     runs-on: ${{ matrix.os }}
     env:
@@ -118,7 +118,7 @@ jobs:
 
   lint:
     name: Lint
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-16core
     steps:
       # Note that we are explicitly NOT checking out submodules, to validate
       # that we haven't accidentally enabled spirv-tools native compilation