utils: introduce a ToolchainInfo.plist on Windows

This allows us to add an identifier to the toolchain on Windows similar
to the swift.org toolchains generated on macOS. The newly introduced
identifiers should help support having parallel installable toolchains.

Author: compnerd

utils/build.ps1

@@ -124,6 +124,7 @@ param(
   [string[]] $AndroidSDKs = @(),
   [string[]] $WindowsSDKs = @("X64","X86","Arm64"),
   [string] $ProductVersion = "0.0.0",
+  [string] $ToolchainVersion = $(if (${env:TOOLCHAIN_VERSION}) { "${env:TOOLCHAIN_VERSION}" } else { "${env:USERNAME}.development" }),
   [string] $PinnedBuild = "",
   [string] $PinnedSHA256 = "",
   [string] $PinnedVersion = "",
@@ -1533,6 +1534,9 @@ function Build-Compilers() {
         "cmark-gfm_DIR" = "$($Arch.ToolchainInstallRoot)\usr\lib\cmake";
       })
   }
+
+  Invoke-Program "$(Get-PythonExecutable)" -c "import plistlib; print(str(plistlib.dumps({ 'Identifier': '${ToolchainIdentifier}' }), encoding='utf-8'))" `
+      -OutFile "$(Arch.ToolchainInstallRoot)\ToolchainInfo.plist"
 }
 
 # Reference: https://github.com/microsoft/mimalloc/tree/dev/bin#minject