add -fpic to CC flags when we build libbusybox (14% smaller .so)

diff --git a/Makefile.flags b/Makefile.flags
index 5294915..243f095 100644
--- a/Makefile.flags
+++ b/Makefile.flags
@@ -56,6 +56,12 @@
 CFLAGS += $(call cc-option,-g)
 endif
 
+# on i386: 14% smaller libbusybox.so
+# (code itself is 9% bigger, we save on relocs/PLT/GOT)
+ifeq ($(CONFIG_BUILD_LIBBUSYBOX),y)
+CFLAGS += -fpic
+endif
+
 ifeq ($(CONFIG_STATIC),y)
 LDFLAGS += -static
 endif