[clang][lit] Allow test cases to use the compiler that are used to compile Clang

[OikawaKirie]

Summary

Required by D83660. Test cases may want to use the host compiler to compile some mocks for the test case. This patch adds two substitutions %host_cc and %host_cxx to use the host compilers set via variable CMAKE_C_COMPILER and CMAKE_CXX_COMPILER.

[steakhal]

Oh, wait a minute. The config.host_cxx was already there.
Where is the symmetry :D It looks much better now, thanks.

Regarding D83660, I'm really looking forward to it. It's a shame that it takes so long to land it.

[OikawaKirie]

In D98918#2636735, @steakhal wrote:

Oh, wait a minute. The config.host_cxx was already there.
Where is the symmetry :D It looks much better now, thanks.

Sounds not bad if it matters to you :P

Regarding D83660, I'm really looking forward to it. It's a shame that it takes so long to land it.

Please commit this patch on my behalf (Ella Ma <[e-mail]>), so that I can continue with D83660 with your mocked solver.

[steakhal]

In D98918#2636790, @OikawaKirie wrote:

Please commit this patch on my behalf (Ella Ma <[e-mail]>), so that I can continue with D83660 with your mocked solver.

Oh, I forgot about this one. My apologies.

clang/test/lit.cfg.py

config.substitutions.append(
          '"%s" %s' % (config.python_executable, check_analyzer_fixit_path)))
 
 llvm_config.add_tool_substitutions(tools, tool_dirs)
 
 config.substitutions.append(
     ('%hmaptool', "'%s' %s" % (config.python_executable,
                              os.path.join(config.clang_tools_dir, 'hmaptool'))))
 
+config.substitutions.append(('%host_cc', config.host_cc))
+config.substitutions.append(('%host_cxx', config.host_cxx))
+
 
 # Plugins (loadable modules)
 if config.has_plugins and config.llvm_plugin_ext:
     config.available_features.add('plugins')
 
 # Set available features we allow tests to conditionalize on.
 #
 if config.clang_default_cxx_stdlib != '':

clang/test/lit.site.cfg.py.in

 config.llvm_plugin_ext = "@LLVM_PLUGIN_EXT@"
 config.lit_tools_dir = path(r"@LLVM_LIT_TOOLS_DIR@")
 config.errc_messages = "@LLVM_LIT_ERRC_MESSAGES@"
 config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
 config.clang_src_dir = path(r"@CLANG_SOURCE_DIR@")
 config.clang_tools_dir = path(r"@CLANG_TOOLS_DIR@")
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
+config.host_cc = "@CMAKE_C_COMPILER@"
 config.host_cxx = "@CMAKE_CXX_COMPILER@"
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.have_zlib = @LLVM_ENABLE_ZLIB@
 config.clang_arcmt = @CLANG_ENABLE_ARCMT@
 config.clang_default_cxx_stdlib = "@CLANG_DEFAULT_CXX_STDLIB@"
 config.clang_staticanalyzer = @CLANG_ENABLE_STATIC_ANALYZER@
 config.clang_staticanalyzer_z3 = "@LLVM_WITH_Z3@"
 config.clang_examples = @CLANG_BUILD_EXAMPLES@