SunOS4 also adds __.SYMDEF to .a files.

config/rules.mk

@@ -553,7 +553,7 @@ else
 AR_LIST		:= ar t
 AR_EXTRACT	:= ar x
 endif
-ifneq (,$(filter OSF1 BSD_OS FreeBSD NetBSD OpenBSD,$(OS_ARCH)))
+ifneq (,$(filter OSF1 BSD_OS FreeBSD NetBSD OpenBSD SunOS,$(OS_ARCH)))
 CLEANUP1	:= | egrep -v '(________64ELEL_|__.SYMDEF)'
 CLEANUP2	:= rm -f ________64ELEL_ __.SYMDEF
 else