[SYCL] Fix passing extra clang flags to lit tests (#4110)

`CFLAGS` is a `make` environment variable so its contents were not used
by the lit tests which call `clang` directly.

Adding them to the `additional_flags` of `use_clang`, adds them to the
`%clangxx` substitutions and ensures they are passed around everywhere.

In addition these extra flags were only set on Linux because they were
used for Linux C++ library assertions, but now they will be set on both
Linux and Windows, however the Linux C++ library assertions defines will
only be set on Linux.

This also allows users to add custom clang parameters to the lit tests
through the `SYCL_CLANG_EXTRA_FLAGS` CMake parameter. Which will be a
requirement for the ROCm AMD lit tests as for AMD the target needs to be
specified with `-mcpu`.

Author: npmiller

sycl/CMakeLists.txt

@@ -147,7 +147,7 @@ function( add_common_options LIB_NAME)
   endif()
 endfunction(add_common_options)
 
-if (LLVM_ENABLE_ASSERTIONS AND NOT SYCL_DISABLE_STL_ASSERTIONS)
+if (LLVM_ENABLE_ASSERTIONS AND NOT SYCL_DISABLE_STL_ASSERTIONS AND NOT WIN32)
   if(SYCL_USE_LIBCXX)
     add_definitions(-D_LIBCPP_DEBUG=1)
     set(SYCL_CLANG_EXTRA_FLAGS "${SYCL_CLANG_EXTRA_FLAGS} -D_LIBCPP_DEBUG=1")

sycl/test/lit.cfg.py

@@ -35,7 +35,7 @@
 # test_exec_root: The root path where tests should be run.
 config.test_exec_root = os.path.join(config.sycl_obj_root, 'test')
 
-llvm_config.use_clang()
+llvm_config.use_clang(additional_flags=config.sycl_clang_extra_flags.split(' '))
 
 # Propagate some variables from the host environment.
 llvm_config.with_system_environment(['PATH', 'OCL_ICD_FILENAMES', 'SYCL_DEVICE_ALLOWLIST', 'SYCL_CONFIG_FILE_NAME'])
@@ -62,8 +62,6 @@
         config.available_features.add('libcxx')
     llvm_config.with_system_environment('LD_LIBRARY_PATH')
     llvm_config.with_environment('LD_LIBRARY_PATH', config.sycl_libs_dir, append_path=True)
-    llvm_config.with_system_environment('CFLAGS')
-    llvm_config.with_environment('CFLAGS', config.sycl_clang_extra_flags)
 
 elif platform.system() == "Windows":
     config.available_features.add('windows')

sycl/test/on-device/lit.cfg.py

@@ -35,7 +35,8 @@
 # test_exec_root: The root path where tests should be run.
 config.test_exec_root = os.path.join(config.sycl_obj_root, 'test')
 
-llvm_config.use_clang(use_installed=True)
+llvm_config.use_clang(use_installed=True,
+                      additional_flags=config.sycl_clang_extra_flags.split(' '))
 
 # Propagate some variables from the host environment.
 llvm_config.with_system_environment(['PATH', 'OCL_ICD_FILENAMES', 'SYCL_DEVICE_ALLOWLIST', 'SYCL_CONFIG_FILE_NAME'])
@@ -57,8 +58,6 @@
     config.available_features.add('linux')
     llvm_config.with_system_environment(['LD_LIBRARY_PATH','LIBRARY_PATH','CPATH'])
     llvm_config.with_environment('LD_LIBRARY_PATH', config.sycl_libs_dir, append_path=True)
-    llvm_config.with_system_environment('CFLAGS')
-    llvm_config.with_environment('CFLAGS', config.sycl_clang_extra_flags)
 
 elif platform.system() == "Windows":
     config.available_features.add('windows')