kbuild: fix build error during make htmldocs

Fix the following build error when do 'make htmldocs':

 DOCPROC Documentation/DocBook/debugobjects.xml
exec /scripts/kernel-doc: No such file or directory
exec /scripts/kernel-doc: No such file or directory

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/basic/docproc.c b/scripts/basic/docproc.c
index 4c9523ef9c00..99ca7a698687 100644
--- a/scripts/basic/docproc.c
+++ b/scripts/basic/docproc.c
@@ -385,7 +385,7 @@ int main(int argc, char *argv[])
         if (!srctree)
                 srctree = getcwd(NULL, 0);
         kernsrctree = getenv("KBUILD_SRC");
-        if (!kernsrctree)
+        if (!kernsrctree || !*kernsrctree)
                 kernsrctree = srctree;
         if (argc != 3) {
                 usage();