Set object extension based on system and not driver used (#1030)

Running tests with clang-cl would set the proper object extension, but
clang and clang++ on Windows would use the wrong .o extension.

Author: mdtoguchi

SYCL/lit.cfg.py

@@ -94,8 +94,10 @@
 config.substitutions.append( ('%sycl_libs_dir',  config.sycl_libs_dir ) )
 if platform.system() == "Windows":
     config.substitutions.append( ('%sycl_static_libs_dir',  config.sycl_libs_dir + '/../lib' ) )
+    config.substitutions.append( ('%obj_ext', '.obj') )
 elif platform.system() == "Linux":
     config.substitutions.append( ('%sycl_static_libs_dir',  config.sycl_libs_dir ) )
+    config.substitutions.append( ('%obj_ext', '.o') )
 config.substitutions.append( ('%sycl_include',  config.sycl_include ) )
 
 if lit_config.params.get('gpu-intel-dg1', False):
@@ -159,7 +161,6 @@
     config.substitutions.append( ('%cxx_std_option',  '/std:' ) )
     config.substitutions.append( ('%fPIC', '') )
     config.substitutions.append( ('%shared_lib', '/LD') )
-    config.substitutions.append( ('%obj_ext', '.obj') )
 else:
     config.substitutions.append( ('%sycl_options', ' -lsycl -I' +
                                 config.sycl_include + ' -I' + os.path.join(config.sycl_include, 'sycl') +
@@ -173,7 +174,6 @@
     # configurations
     config.substitutions.append( ('%fPIC', ('' if platform.system() == 'Windows' else '-fPIC')) )
     config.substitutions.append( ('%shared_lib', '-shared') )
-    config.substitutions.append( ('%obj_ext', '.o') )
 
 if not config.gpu_aot_target_opts:
     config.gpu_aot_target_opts = '"-device *"'