Add <experimental/coroutine>

This patch adds the library portions of the coroutines PDTS,
which should now be supported by Clang.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@303836 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/libcxx/test/config.py b/utils/libcxx/test/config.py
index 2118f9c..2b89a1c 100644
--- a/utils/libcxx/test/config.py
+++ b/utils/libcxx/test/config.py
@@ -142,6 +142,7 @@
         self.configure_sanitizer()
         self.configure_coverage()
         self.configure_modules()
+        self.configure_coroutines()
         self.configure_substitutions()
         self.configure_features()
 
@@ -954,6 +955,10 @@
             self.cxx.flags += ['-g', '--coverage']
             self.cxx.compile_flags += ['-O0']
 
+    def configure_coroutines(self):
+        if self.cxx.hasCompileFlag('-fcoroutines-ts'):
+            self.config.available_features.add('fcoroutines-ts')
+
     def configure_modules(self):
         modules_flags = ['-fmodules']
         if platform.system() != 'Darwin':