libexec/customcc: Ensure the -isysroot argument is not empty.

diff --git a/libexec/customcc/Makefile b/libexec/customcc/Makefile
index 2c0720a..3eff760 100644 (file)
--- a/libexec/customcc/Makefile
+++ b/libexec/customcc/Makefile
@@ -8,6 +8,6 @@ CLEANFILES=     cc
 NOMAN=
 
 ${.OBJDIR}/cc: cc.sh
-       sed "s#@@INCPREFIX@@#${USRDATA_PREFIX}#g" $> > $@
+       sed "s#@@INCPREFIX@@#${USRDATA_PREFIX:S;^$;/;}#g" $> > $@
 
 .include <bsd.prog.mk>