Update Makefile

src/Makefile

@@ -309,7 +309,7 @@ endif
 #  -D_DEFAULT_SOURCE        use with -std=c99 on Linux and PLATFORM_WEB, required for timespec
 #  -Werror=pointer-arith    catch unportable code that does direct arithmetic on void pointers
 #  -fno-strict-aliasing     jar_xm.h does shady stuff (breaks strict aliasing)
-CFLAGS = -Wall -D_DEFAULT_SOURCE -D$(PLATFORM) -D$(GRAPHICS) -Wno-missing-braces -Werror=pointer-arith -fno-strict-aliasing $(CUSTOM_CFLAGS)
+CFLAGS = -Wall -D_GNU_SOURCE -D$(PLATFORM) -D$(GRAPHICS) -Wno-missing-braces -Werror=pointer-arith -fno-strict-aliasing $(CUSTOM_CFLAGS)
 
 ifneq ($(RAYLIB_CONFIG_FLAGS), NONE)
     CFLAGS += -DEXTERNAL_CONFIG_FLAGS $(RAYLIB_CONFIG_FLAGS)