Teach tgmath.h to only include <complex.h> if it's available.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149213 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Headers/tgmath.h b/lib/Headers/tgmath.h
index 1b0b9d2..554af6c 100644
--- a/lib/Headers/tgmath.h
+++ b/lib/Headers/tgmath.h
@@ -30,7 +30,9 @@
/* C++ handles type genericity with overloading in math.h. */
#ifndef __cplusplus
-#include <complex.h>
+#if __has_include(<complex.h>)
+# include <complex.h>
+#endif
#define _TG_ATTRSp __attribute__((__overloadable__))
#define _TG_ATTRS __attribute__((__overloadable__, __always_inline__))