Add comment why --gc-sections is ignored

Rules.mak

@@ -358,6 +358,7 @@ endif
 #CFLAGS += $(call check_gcc,-std=c99,)
 
 LDFLAGS_NOSTRIP:=$(CPU_LDFLAGS-y) -shared --warn-common --warn-once -z combreloc
+# binutils-2.16.1 warns about ignored sections, 2.16.91.0.3 and newer are ok
 #LDFLAGS_NOSTRIP+=$(call check_ld,--gc-sections)
 
 ifeq ($(UCLIBC_BUILD_RELRO),y)