lib9: handle empty TMPDIR more gracefully.

Before, an empty TMPDIR would lead to:
cannot create <nil>/go.o: No such file or directory

R=golang-dev, iant, dave, bradfitz
CC=golang-dev
https://golang.org/cl/8355045

diff --git a/src/lib9/tempdir_unix.c b/src/lib9/tempdir_unix.c
index 7b7e58b4d061a3b28873552f5783b79d015929d7..99a7092b68b09797477e4b7a27063734ca28e603 100644 (file)
--- a/src/lib9/tempdir_unix.c
+++ b/src/lib9/tempdir_unix.c
@@ -16,7 +16,7 @@ mktempdir(void)
        char *tmp, *p;
        
        tmp = getenv("TMPDIR");
-       if(tmp == nil)
+       if(tmp == nil || strlen(tmp) == 0)
                tmp = "/var/tmp";
        p = smprint("%s/go-link-XXXXXX", tmp);
        if(mkdtemp(p) == nil)