Add library search paths on windows

Author: vladimirlaz

SYCL/Basic/lit.cfg.py

@@ -54,6 +54,8 @@
     config.available_features.add('windows')
     llvm_config.with_system_environment('LIB')
     llvm_config.with_environment('LIB', config.sycl_libs_dir, append_path=True)
+    llvm_config.with_environment('PATH', config.sycl_libs_dir, append_path=True)
+    llvm_config.with_environment('LIB', os.path.join(dpcpp_root_dir, 'lib'), append_path=True)
 
 elif platform.system() == "Darwin":
     # FIXME: surely there is a more elegant way to instantiate the Xcode directories.