atomic: fix __GNUC_PREREQ compilation error on musl
@@ -25,7 +25,7 @@ extern "C" {
#define __CLANG_ATOMICS
#elif defined(__GNUC__)
-#if __GNUC_PREREQ(4, 9)
+#if (__GNUC__ << 16) + __GNUC_MINOR__ >= 0x40009
#define __SYNC_ATOMICS
#else
#error "Atomic requires gcc >= 4.9"
