--- gcc-6.3.0-A/gcc/system.h
+++ gcc-6.3.0-B/gcc/system.h
@@ -819,7 +819,8 @@
 #ifndef USES_ISL
 #undef calloc
 #undef strdup
- #pragma GCC poison calloc strdup
+/* Do not poison calloc because it is declared in musl's sched.h */
+ #pragma GCC poison strdup
 #endif
 
 #if !defined(FLEX_SCANNER) && !defined(YYBISON)