make sure we re-use the existing CFLAGS settings so that we get all the right
flags (like -fno-stack-protector).  just append the few changes we want (the
optimization levels).

https://bugs.gentoo.org/590974

--- a/Makefile
+++ b/Makefile
@@ -65,7 +65,7 @@
 	$(CC) -Wall -Werror -march=i486 -m32 -O0 -fomit-frame-pointer -fno-builtin -ffreestanding -fPIC $(SMP_FL) -fno-stack-protector   -c -o memsize.o memsize.c
 
 random.o: random.c
-	$(CC) -c -Wall -march=i486 -m32 -O3 -fomit-frame-pointer -fno-builtin -ffreestanding random.c
+random.o: CFLAGS += -O3 -fno-PIC
 
 clean:
 	rm -f *.o *.s *.iso memtest.bin memtest memtest_shared \