build warning

[benesch]

From our builder image:

[15:58:02][Step 2/3] # github.com/cockroachdb/cockroach/vendor/github.com/knz/go-libedit/unix
[15:58:02][Step 2/3] In file included from wrap-common.c:1:
[15:58:02][Step 2/3] In file included from vendor/github.com/knz/go-libedit/unix/src/libedit-common.c:1:
[15:58:02][Step 2/3] vendor/github.com/knz/go-libedit/unix/src/c-libedit/common.c:371:21: warning: passing 'wint_t *' (aka 'unsigned int *') to parameter of type 'wchar_t *' (aka 'int *') converts between pointers to integer types with different sign [-Wpointer-sign]
[15:58:02][Step 2/3] vendor/github.com/knz/go-libedit/unix/src/c-libedit/histedit.h:267:37: note: passing argument to parameter here

Doesn't seem to be causing any harm, but would be nice to clean up if there's an easy fix!