[WindowsDriver] Always consider WinSdkVersion (#130377)

Currently, the `-Xmicrosoft-windows-sdk-version` is only used if
`-Xmicrosoft-windows-sdk-root` is also provided. This is a surprising
behavior since the argument should still be taking effect if LLVM uses
the Windows SDK root from the registry.

Tested locally in a simple Hello World program including `Windows.h` and
compiled with `-Xmicrosoft-windows-sdk-version 10.0.18362.0` on a system
where the SDK 10.0.22621.0 is also installed and verified that the
correct header was included.

Co-authored-by: Saleem Abdulrasool <[email protected]>

Author: Steelskin

llvm/lib/WindowsDriver/MSVCPaths.cpp

@@ -444,6 +444,13 @@ bool getWindowsSDKDir(vfs::FileSystem &VFS, std::optional<StringRef> WinSdkDir,
     return !WindowsSDKLibVersion.empty();
   }
   if (Major == 10) {
+    if (WinSdkVersion) {
+      // Use the user-provided version as-is.
+      WindowsSDKIncludeVersion = WinSdkVersion->str();
+      WindowsSDKLibVersion = WindowsSDKIncludeVersion;
+      return true;
+    }
+
     if (!getWindows10SDKVersionFromPath(VFS, Path, WindowsSDKIncludeVersion))
       return false;
     WindowsSDKLibVersion = WindowsSDKIncludeVersion;
@@ -475,6 +482,12 @@ bool getUniversalCRTSdkDir(vfs::FileSystem &VFS,
           Path, nullptr))
     return false;
 
+  if (WinSdkVersion) {
+    // Use the user-provided version as-is.
+    UCRTVersion = WinSdkVersion->str();
+    return true;
+  }
+
   return getWindows10SDKVersionFromPath(VFS, Path, UCRTVersion);
 }