For mkcsmapper, conditionalize gcc-specific compile flags.

MFC after:	3 days

usr.bin/mkcsmapper/Makefile.inc

@@ -1,7 +1,11 @@
 # $FreeBSD$
 
+.include <bsd.compiler.mk>
+
 SRCS+=	lex.l yacc.y
 CFLAGS+= -I${.CURDIR} -I${.CURDIR}/../mkcsmapper \
 	 -I${.CURDIR}/../../lib/libc/iconv \
-	 -I${.CURDIR}/../../lib/libiconv_modules/mapper_std \
-	 --param max-inline-insns-single=64
+	 -I${.CURDIR}/../../lib/libiconv_modules/mapper_std
+.if ${COMPILER_TYPE} == "gcc"
+CFLAGS+= --param max-inline-insns-single=64
+.endif