[libc++] Set filesystem test flags in a lit.local.cfg

[ldionne]

Summary

This reduces the complexity of our already complex global lit configuration,
and also avoids cluttering the compilation commands for all tests with
things that are only relevant to the filesystem tests.

[ldionne]

Make sure we don't modify the cxx compiler flags globally

[ldionne]

Don't set the dynamic test root, since that's not required if we're based on
the parent change. Apologies for the frantic updates, I have many outstanding
patches and my git got somewhat messed up.

libcxx/test/std/input.output/filesystems/lit.local.cfg

+import copy
+import os
+import sys
+
 # Disable all of the filesystem tests if the dylib under test doesn't support them.
 if 'dylib-has-no-filesystem' in config.available_features:
   config.unsupported = True
 if 'c++filesystem-disabled' in config.available_features:
   config.unsupported = True
+
+config.test_format.cxx = copy.deepcopy(config.test_format.cxx)
+
+inputs = os.path.join(os.path.dirname(__file__), 'Inputs', 'static_test_env')
+config.test_format.cxx.compile_flags += ['-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="{}"'.format(inputs)]
+
+dynamic_helper = os.path.join(config.test_source_root, 'support', 'filesystem_dynamic_test_helper.py')
+assert os.path.isfile(dynamic_helper)
+config.test_format.cxx.compile_flags += ['-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="{} {}"'.format(sys.executable, dynamic_helper)]

libcxx/utils/libcxx/test/config.py

def configure(self):
         self.configure_obj_root()
         self.configure_cxx_stdlib_under_test()
         self.configure_cxx_library_root()
         self.configure_use_clang_verify()
         self.configure_use_thread_safety()
         self.configure_execute_external()
         self.configure_ccache()
         self.configure_compile_flags()
-        self.configure_filesystem_compile_flags()
         self.configure_link_flags()
         self.configure_env()
         self.configure_color_diagnostics()
         self.configure_debug_mode()
         self.configure_warnings()
         self.configure_sanitizer()
         self.configure_coverage()
         self.configure_modules()
def configure_compile_flags_abi_version(self):
         # Only add the ABI version when it is non-default.
         # FIXME(EricWF): Get the ABI version from the "__config_site".
         if abi_version and abi_version != '1':
           self.cxx.compile_flags += ['-D_LIBCPP_ABI_VERSION=' + abi_version]
         if abi_unstable:
           self.config.available_features.add('libcpp-abi-unstable')
           self.cxx.compile_flags += ['-D_LIBCPP_ABI_UNSTABLE']
 
-    def configure_filesystem_compile_flags(self):
-        static_env = os.path.join(self.libcxx_src_root, 'test', 'std',
-                                  'input.output', 'filesystems', 'Inputs', 'static_test_env')
-        static_env = os.path.realpath(static_env)
-        assert os.path.isdir(static_env)
-        self.cxx.compile_flags += ['-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="%s"' % static_env]
-
-        dynamic_helper = os.path.join(self.libcxx_src_root, 'test', 'support',
-                                      'filesystem_dynamic_test_helper.py')
-        assert os.path.isfile(dynamic_helper)
-
-        self.cxx.compile_flags += ['-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="%s %s"'
-                                   % (sys.executable, dynamic_helper)]
-
-
     def configure_link_flags(self):
         # Configure library path
         self.configure_link_flags_cxx_library_path()
         self.configure_link_flags_abi_library_path()
 
         # Configure libraries
         if self.cxx_stdlib_under_test == 'libc++':
             self.cxx.link_flags += ['-nodefaultlibs']