ci(amd64/msvc): source vsdevcmd.bat

tools/ci/amd64/msvc/unit_tests.ps1

@@ -1,5 +1,8 @@
 # @ref https://learn.microsoft.com/en-us/cpp/build/reference/compiler-options-listed-by-category
 
+# @todo(Light): Pull this from an environment variable
+& "C:\Program Files\Microsoft Visual Studio\18\Enterprise\Common7\Tools\VsDevCmd.bat"
+
 if (Test-Path "./build") {
     Remove-Item "./build" -r -force
 }