Allow compilation on both beta4 and nightlies with a fixed features.h

etc/makefile.main

@@ -19,7 +19,19 @@ FASTTRAX_DIR := FastTrax
 OPTIMIZER		=	-O3
 
 CC		     	:=	gcc
-CFLAGS			 =	$(OPTIMIZER) -Wall -Wno-multichar -Wno-ctor-dtor-privacy -D__USE_GNU -DSTDC_HEADERS
+
+# This is needed to be able to compile on either nightlies, or beta4.
+# See https://dev.haiku-os.org/ticket/11818 (fixed for good in hrev57497).
+# We can simplify this once the haikuports buildmasters switch to beta5.
+
+HAIKU_HREV_NUM = $(shell uname -v | cut -d " " -f 1 | cut -d "+" -f 1 | sed s/hrev//)
+HAS_FIXED_FEATURES_H = $(shell if [ $(strip $(HAIKU_HREV_NUM)) -ge 57497 ]; then echo "YES"; else echo "NO"; fi)
+
+ifeq ($(strip $(HAS_FIXED_FEATURES_H)), YES)
+	CFLAGS	=	$(OPTIMIZER) -Wall -Wno-multichar -Wno-ctor-dtor-privacy -D_DEFAULT_SOURCE -DSTDC_HEADERS
+else
+	CFLAGS	=	$(OPTIMIZER) -Wall -Wno-multichar -Wno-ctor-dtor-privacy -D__USE_GNU -DSTDC_HEADERS
+endif
 
 LD				:=	gcc
 LDFLAGS			:=