Index: lib/CMakeLists.txt
===================================================================
--- lib/CMakeLists.txt
+++ lib/CMakeLists.txt
@@ -51,6 +51,13 @@
 
 # Setup flags.
 append_if(compile_flags LIBCXX_HAS_FPIC_FLAG -fPIC)
+# If -nostdinc++ is present, then remove it from CMAKE_CXX_FLAGS and
+# move it to compile_flags so that it doesn't get passed to the linker
+# and cause an unused flag warning.
+if (LIBCXX_HAS_NOSTDINCXX_FLAG)
+  list(APPEND compile_flags -nostdinc++)
+  string(REPLACE "-nostdinc++" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+endif()
 append_if(link_flags LIBCXX_HAS_NODEFAULTLIBS_FLAG -nodefaultlibs)
 
 if ( APPLE )