[libc++] Disable local submodule visibility in the modules build

[ldionne]

This was discussed in https://reviews.llvm.org/D119036. I suspect this won't pass, but I want to see what CI will say.

[ldionne]

Try to remove textual for config and config_site, which is what's causing problems with LLDB.

[aprantl]

libcxx/utils/libcxx/test/params.py

74

I don't really understand the libcxx test configuration, but it looks like this changes the test that the std module can be built to not use LSV. Should we maybe test both LSV and non-LSV configs going forward?

[ldionne]

libcxx/utils/libcxx/test/params.py

74

Honestly, I'd rather just test the default -fmodules flag, that's it. I don't even know why we had LSV turned on previously. I have no desire to start supporting various ways to build with modules, just whatever the default modules build is. We don't really have that much CI hardware to spare.

[ldionne]

I'm going to ship this since it looks like CI is happy with it.

libcxx/include/module.modulemap

 // define the module for __config outside of the top level 'std' module
 // since __config may be included from C headers which may create an
 // include cycle.
 module std_config [system] [extern_c] {
-  textual header "__config"
-  textual header "__config_site"
+  header "__config"
+  header "__config_site"
+  export *
 }
 
 module std [system] {
   export std_config
   // FIXME: The standard does not require that each of these submodules
   // re-exports its imported modules. We should provide an alternative form of
   // export that issues a warning if a name from the submodule is used, and
   // use that to provide a 'strict mode' for libc++.

libcxx/utils/libcxx/test/params.py

DEFAULT_PARAMETERS = [
   Parameter(name='std', choices=_allStandards, type=str,
             help="The version of the standard to compile the test suite with.",
             default=lambda cfg: next(s for s in reversed(_allStandards) if getStdFlag(cfg, s)),
             actions=lambda std: [
               AddFeature(std),
               AddCompileFlag(lambda cfg: getStdFlag(cfg, std)),
             ]),
 
   Parameter(name='enable_modules', choices=[True, False], type=bool, default=False,
             help="Whether to build the test suite with Clang modules enabled.",
             actions=lambda modules: [
               AddFeature('modules-build'),
               AddCompileFlag('-fmodules'),
-              AddCompileFlag('-Xclang -fmodules-local-submodule-visibility'),
             ] if modules else []),
 
   Parameter(name='enable_exceptions', choices=[True, False], type=bool, default=True,
             help="Whether to enable exceptions when compiling the test suite.",
             actions=lambda exceptions: [] if exceptions else [
               AddFeature('no-exceptions'),
               AddCompileFlag('-fno-exceptions')
             ]),