Add support for Windows arm64 (#423)

.github/workflows/build_windows.yaml

@@ -14,7 +14,7 @@ on:
             arch:
                 type: string
                 required: true
-                description: "The architecture to build for, one of 'x64' | 'x86'"
+                description: "The architecture to build for, one of 'x64' | 'x86' | 'arm64'"
             version:
                 type: string
                 required: false
@@ -45,6 +45,12 @@ jobs:
                           "target": "x86_64-pc-windows-msvc",
                           "dir": "x64"
                         },
+                        "arm64": {
+                          "target": "aarch64-pc-windows-msvc",
+                          "build-args": "--arm64",
+                          "arch": "amd64_arm64",
+                          "dir": "arm64"
+                        },
                         "x86": {
                           "target": "i686-pc-windows-msvc",
                           "build-args": "--ia32",
@@ -69,7 +75,7 @@ jobs:
             - name: Set up build tools
               uses: ilammy/msvc-dev-cmd@v1
               with:
-                  arch: ${{ inputs.arch }}
+                  arch: ${{ steps.config.outputs.arch || inputs.arch }}
 
             # ActiveTCL package on choco is from 2015,
             # this one is newer but includes more than we need