Fix build script errors

No longer errors when vcpkg path not specified.

mk/windoze/build-mg-vs-cmake.ps1

@@ -69,13 +69,13 @@ git pull
 Write-Title "Setup vcpkg"
 Test-Command "cmake" "Please download and install CMake: https://cmake.org/download/. (For 64 bit windows, select 'cmake-x.y.z-windows-x86_64.msi'.)"
 
-${vcpkg-location} = $(Resolve-Path ${vcpkg-location}).ToString()
-"path is ${vcpkg-location}"
-
 if ( !${vcpkg-location} ) {
     ${vcpkg-location} = Join-Path $PSScriptRoot \vcpkg
     "Vcpkg location not set. Setting it to ${vcpkg-location}."
 }
+else {
+    ${vcpkg-location} = $(Resolve-Path ${vcpkg-location}).ToString()
+}
 
 if ( Test-Path ${vcpkg-location} ) {
     "Found vcpkg."