HEAD buildworld fails in libc

I don't know why this hasn't already been reported, but I've been
seeing this error since the commit was made.

===> lib/libc (obj,all,install)
/usr/src/lib/libc/string/strerror.c:96:11: error: passing 'const char []' to parameter of type 'char *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
                        __uprefix,
                        ^~~~~~~~~
/usr/src/lib/libc/string/strerror.c:61:23: note: passing argument to parameter 'uprefix' here
errstr(int num, char *uprefix, char *buf, size_t len)
                      ^
1 error generated.
*** [strerror.o] Error code 1

I deleted /usr/obj, disabled META_MODE and ran the ``make buildworld''
with -j1.

My /usr/src is at r342569.

-- 
Gary Jennejohn