cmd/dist: more informative error for mkdtemp failing

The Darwin builders are all failing here but strerror doesn't provide context.

R=golang-dev, bradfitz, adg
CC=golang-dev
https://golang.org/cl/13095043

diff --git a/src/cmd/dist/unix.c b/src/cmd/dist/unix.c
index 41ae19498ee8019d233c60cb31b8e0bcbfadfadf..4a4feeb06455c63f319a3d998d1f1085d1f21476 100644 (file)
--- a/src/cmd/dist/unix.c
+++ b/src/cmd/dist/unix.c
@@ -467,8 +467,9 @@ xworkdir(void)
        if(b.len == 0)
                bwritestr(&b, "/var/tmp");
        bwritestr(&b, "/go-cbuild-XXXXXX");
-       if(mkdtemp(bstr(&b)) == nil)
-               fatal("mkdtemp: %s", strerror(errno));
+       p = bstr(&b);
+       if(mkdtemp(p) == nil)
+               fatal("mkdtemp(%s): %s", p, strerror(errno));
        p = btake(&b);
 
        bfree(&b);