[libcxx] [test] Move the is_<platform> functions down to subclasses

[mstorsjo]

Summary

If cross testing (and manually specifying a LIBCXX_TARGET_INFO in the
cmake configuration, as the default is to match the build platform),
we want the accessors for querying the target platform, is_windows,
is_darwin, to return the right value depending on which target info
class is used, not based on what platform is running the build and
driving the tests.

When LIBCXX_TARGET_INFO isn't defined, the right target info class
is chosen automatically based on the platform one is running on, so
this shouldn't make any practical difference for such setups.

[curdeius]

LGTM. Hopefully that doesn't break any "exotic" setups.

libcxx/utils/libcxx/test/target_info.py

24–25

Just a remark. No action needed.
platform() (here and in LinuxLocalTI) seems unused now unless I'm mistaken.
But it seems it's the case of some other methods especially in LinuxLocalTI.

[ldionne]

LGTM, but FYI the whole target_into.py and even config.py will eventually be replaced by simpler setups like libcxx/test/configs/libcxx-trunk-shared.cfg.in. It's a slow process but I've been chipping at it little by little.

[mstorsjo]

In D98045#2606909, @ldionne wrote:

LGTM, but FYI the whole target_into.py and even config.py will eventually be replaced by simpler setups like libcxx/test/configs/libcxx-trunk-shared.cfg.in. It's a slow process but I've been chipping at it little by little.

Ok, that sounds good to me, I'm not particularly attached to the current way of things, as long as the new setup is something that is flexible enough (and it looks like its) for oddball setups :-)

[mstorsjo]

Reuploading to retry CI (last round had a fair bit of spurious breakage)

libcxx/utils/libcxx/test/target_info.py

 
 from libcxx.util import executeCommand
 
 class DefaultTargetInfo(object):
     def __init__(self, full_config):
         self.full_config = full_config
         self.executor = None
 
     def platform(self):
         return sys.platform.lower().strip()
 
     def is_windows(self):
-        return self.platform() == 'win32'
+        return False
 
     def is_mingw(self):
         return False
 
     def is_darwin(self):
-        return self.platform() == 'darwin'
+        return False
 
     def add_cxx_flags(self, flags): pass
     def add_cxx_compile_flags(self, flags): pass
     def add_cxx_link_flags(self, flags): pass
     def allow_cxxabi_link(self): return True
 
     def add_path(self, dest_env, new_path):
         if not new_path:
             return
         if 'PATH' not in dest_env:
             dest_env['PATH'] = new_path
         else:
             split_char = ';' if self.is_windows() else ':'
             dest_env['PATH'] = '%s%s%s' % (new_path, split_char,
                                            dest_env['PATH'])
 
 
 class DarwinLocalTI(DefaultTargetInfo):
     def __init__(self, full_config):
         super(DarwinLocalTI, self).__init__(full_config)
 
+    def is_darwin(self):
+        return True
+
     def is_host_macosx(self):
         name = lit.util.to_string(subprocess.check_output(['sw_vers', '-productName'])).strip()
         return name == "Mac OS X"
 
     def get_macosx_version(self):
         assert self.is_host_macosx()
         version = lit.util.to_string(subprocess.check_output(['sw_vers', '-productVersion'])).strip()
         version = re.sub(r'([0-9]+\.[0-9]+)(\..*)?', r'\1', version)

 class LinuxRemoteTI(LinuxLocalTI):
     def __init__(self, full_config):
         super(LinuxRemoteTI, self).__init__(full_config)
 
 class WindowsLocalTI(DefaultTargetInfo):
     def __init__(self, full_config):
         super(WindowsLocalTI, self).__init__(full_config)
 
+    def is_windows(self):
+        return True
+
 class MingwLocalTI(WindowsLocalTI):
     def __init__(self, full_config):
         super(MingwLocalTI, self).__init__(full_config)
 
     def is_mingw(self):
         return True
 
 def make_target_info(full_config):