Test __GLIBC__ is defined before using its value.

Avoids -Wundef warning.

Change-Id: I52d8223500fe31cdf7023e32e96df75e33eb2f7e
diff --git a/core/combo/include/arch/linux-x86/AndroidConfig.h b/core/combo/include/arch/linux-x86/AndroidConfig.h
index a8d74fd..1f2d9ab 100644
--- a/core/combo/include/arch/linux-x86/AndroidConfig.h
+++ b/core/combo/include/arch/linux-x86/AndroidConfig.h
@@ -256,7 +256,7 @@
 /*
  * Define to 1 if <stdlib.h> provides qsort_r() with a GNU style function prototype.
  */
-#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 8)
+#if defined(__GLIBC__) && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 8))
 #define HAVE_GNU_QSORT_R 1
 #else
 #define HAVE_GNU_QSORT_R 0