Fix handling of -Wno-pedantic

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@250452 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1d46e28..7017ce4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -219,8 +219,9 @@
              -stdlib=libc++ -stdlib=libstdc++ -lc++abi -m32)
 
 # FIXME(EricWF): See the FIXME on LIBCXX_ENABLE_PEDANTIC.
-# Remove the -pedantic flag provided by LLVM.
-remove_flags(-pedantic)
+# Remove the -pedantic flag and -Wno-pedantic and -pedantic-errors
+# so they don't get transformed into -Wno and -errors respectivly.
+remove_flags(-Wno-pedantic -pedantic-errors -pedantic)
 
 # Required flags ==============================================================
 add_compile_flags_if_supported(-std=c++11)