+$(OBJROOT)/runtime/objc-rtp-sym.x86_64.o: $(SRCROOT)/runtime/objc-rtp-sym.s
+ $(SILENT) $(CC) $(CFLAGS_OPTIMIZED) -arch x86_64 "$<" -c -o "$@.temp"
+ $(SILENT) $(STRIP) -S "$@.temp"
+ $(SILENT) $(LD) -arch x86_64 -seg1addr 0xfffffffffffec000 "$@.temp" -r -o "$@"
+
+# Additional rule: markgc tool to pretend we compiled with GC write-barriers
+$(MARKGC): $(SRCROOT)/markgc.c
+ $(SILENT) $(ECHO) "Building markgc tool ..."
+ $(SILENT) $(CC) -std=gnu99 "$<" -o "$@"
+
+# Additional linkage: LP64 targets require libstdc++
+LIBS_ppc64 = -lstdc++
+LIBS_x86_64 = -lstdc++