Add comment about duplication of EXTRA_PARTS in EXTRA_MULTILIB_PARTS

From-SVN: r25999

gcc/config/arm/t-arm-elf

@@ -2,8 +2,6 @@ CROSS_LIBGCC1 = libgcc1-asm.a
 LIB1ASMSRC = arm/lib1funcs.asm
 LIB1ASMFUNCS = _udivsi3 _divsi3 _umodsi3 _modsi3 _dvmd_tls
 
-EXTRA_PARTS = crtbegin.o crtend.o
-
 # These are really part of libgcc1, but this will cause them to be
 # built correctly, so...
 
@@ -31,4 +29,7 @@ dp-bit.c: $(srcdir)/config/fp-bit.c
 # LIBGCC = stmp-multilib
 # INSTALL_LIBGCC = install-multilib
 
+# If EXTRA_MULTILIB_PARTS is not defined above then define EXTRA_PARTS here
+EXTRA_PARTS = crtbegin.o crtend.o
+
 TARGET_LIBGCC2_CFLAGS = -Dinhibit_libc