Add SafeStack support for test-suite.

[tharvik]

Remove SafeStack from new-delete feature.

[tharvik]

When running the test suite, it gives a bunch of undefined reference to '__safestack_unsafe_stack_ptr'.
See regression results.

[jroelofs]

LGTM

[jroelofs]

In D13465#260628, @tharvik wrote:

When running the test suite, it gives a bunch of undefined reference to '__safestack_unsafe_stack_ptr'.
See regression results.

Sounds like it's missing the safestack runtime, which should be provided by building compiler-rt.

[tharvik]

In D13465#260846, @jroelofs wrote:

In D13465#260628, @tharvik wrote:

When running the test suite, it gives a bunch of undefined reference to '__safestack_unsafe_stack_ptr'.
See regression results.

Sounds like it's missing the safestack runtime, which should be provided by building compiler-rt.

If you try to build compiler-rt, with safestack forced, you end up with some "already define" error, because safestack use interception which is needed by some tests. We can make these tests as excepted failure though.

test/libcxx/test/config.py

def configure_sanitizer(self):
                 self.cxx.compile_flags += ['-O3']
                 self.config.available_features.add('ubsan')
                 if self.target_info.platform() == 'darwin':
                     self.config.available_features.add('sanitizer-new-delete')
             elif san == 'Thread':
                 self.cxx.flags += ['-fsanitize=thread']
                 self.config.available_features.add('tsan')
                 self.config.available_features.add('sanitizer-new-delete')
+            elif san == 'SafeStack':
+                self.cxx.flags += ['-fsanitize=safe-stack']
+                self.config.available_features.add('safestack')
             else:
                 self.lit_config.fatal('unsupported value for '
                                       'use_sanitizer: {0}'.format(san))
             san_lib = self.get_lit_conf('sanitizer_library')
             if san_lib:
                 self.cxx.link_flags += [
                     san_lib, '-Wl,-rpath,%s' % os.path.dirname(san_lib)]