misdetected on musl...

--- third_party/vulkan-validation-layers/src/loader/loader.c.orig	2017-07-25 19:06:31.000000000 +0000
+++ third_party/vulkan-validation-layers/src/loader/loader.c	2017-07-27 16:20:54.721755713 +0000
@@ -214,9 +214,9 @@
     // the inst pointer to get rid of compiler warnings.
     (void)inst;
 
-#ifdef HAVE_SECURE_GETENV
+#if defined(HAVE_SECURE_GETENV) && defined(__GLIBC__)
     return secure_getenv(name);
-#elif defined(HAVE___SECURE_GETENV)
+#elif defined(HAVE___SECURE_GETENV) && defined(__GLIBC__)
     return __secure_getenv(name);
 #else
 #pragma message("Warning:  Falling back to non-secure getenv for environmental lookups!  Consider" \
