Otherwise a second configure run will totally miss out the setting of
BUILD_INC. I made the link -sf as it seemed the easier way around.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 configure | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 1dc527b..c622a5e 100755
--- a/configure
+++ b/configure
@@ -176,10 +176,10 @@ fi
 
 # Are we in a separate build tree? If so, link the Makefile
 # so that 'make' works.
-if test ! -e Makefile; then
+if test ! -e Makefile || test -s Makefile; then
     echo "linking Makefile..."
     BUILD_INC="-I $(pwd)"
-    ln -s "${SRCDIR}/Makefile" .
+    ln -sf "${SRCDIR}/Makefile" .
 fi
 
 generate_config
-- 
2.14.2