[libcxx] Disable -Wconstant-evaluated for testsuite

[EricWF]

Why was this committed without review?

Why are we ignoring this warning instead of fixing it?

[xbolva00]

Yes, it was commited to fix red buildbot (libc++’s buildbot uses -Werror).

Warning did not reveal any real bugs in testsuite. It warned for cases which are tautologically true/false but it makes sense to have such tests in libc++ testsuite. So turning off warning looked as a reasonable decision.

libcxx/utils/libcxx/test/config.py

def configure_warnings(self):
             '-Wall', '-Wextra', '-Werror'
         ]
         if self.cxx.hasWarningFlag('-Wuser-defined-warnings'):
             self.cxx.warning_flags += ['-Wuser-defined-warnings']
             self.config.available_features.add('diagnose-if-support')
         self.cxx.addWarningFlagIfSupported('-Wshadow')
         self.cxx.addWarningFlagIfSupported('-Wno-unused-command-line-argument')
         self.cxx.addWarningFlagIfSupported('-Wno-attributes')
+        self.cxx.addWarningFlagIfSupported('-Wno-constant-evaluated')
         self.cxx.addWarningFlagIfSupported('-Wno-pessimizing-move')
         self.cxx.addWarningFlagIfSupported('-Wno-c++11-extensions')
         self.cxx.addWarningFlagIfSupported('-Wno-user-defined-literals')
         self.cxx.addWarningFlagIfSupported('-Wno-noexcept-type')
         self.cxx.addWarningFlagIfSupported('-Wno-aligned-allocation-unavailable')
         # These warnings should be enabled in order to support the MSVC
         # team using the test suite; They enable the warnings below and
         # expect the test suite to be clean.