diff --git a/libexec/qt-internal-configure-tests.bat.in b/libexec/qt-internal-configure-tests.bat.in
index 9dfae90ee7d..6b69910c669 100644
--- a/libexec/qt-internal-configure-tests.bat.in
+++ b/libexec/qt-internal-configure-tests.bat.in
@@ -3,12 +3,25 @@ setlocal ENABLEDELAYEDEXPANSION ENABLEEXTENSIONS
 set script_dir_path=%~dp0
 set script_dir_path=%script_dir_path:~0,-1%
 
-rem add the drive letter to the source_dir_path,
-rem by removing the path argument, expanding it, and adding it back
-set source_dir_path=%~dpnx1
+rem Extracts the source path, make it native, and put it
+rem back again. This is a workaround on Windows LLVM/MINGW
+rem to help CMake find source files when doing Unity Build.
 set args=%*
-set args=%args:* =%
-set args=%source_dir_path% %args%
+set source_dir_path=
+set native_source_dir_path=
+for %%i in (%args%) do (
+    if "%%i"=="-S" (
+        set found=true
+    ) else if defined found (
+        set source_dir_path=%%i
+        set native_source_dir_path=%%~dpnxi
+        set found=
+    )
+)
+
+if NOT "%native_source_dir_path%" == "" (
+    set args=!args:%source_dir_path%=%native_source_dir_path%!
+)
 
 set cmake_scripts_dir=%script_dir_path%