Build system: Fix ./build debian

We need to -I and -L the build tree directories, not the directories
in /usr/local or wheveever.  Otherwise (a) the `./debian build' fails
if wiringPi is not installed (b) if it _is_ installed, the build picks
up the installed versions rather than the versions being built, which
is wrong.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

build

@@ -82,9 +82,9 @@ if [ x$1 = "xdebian" ]; then
   cd $here/wiringPi
   make install-deb
   cd $here/devLib
-  make install-deb
+  make install-deb INCLUDE='-I. -I../wiringPi'
   cd $here/gpio
-  make install-deb
+  make install-deb INCLUDE='-I../wiringPi -I../devLib' LDFLAGS=-L../debian/wiringPi/usr/lib
   cd $here/debian
   fakeroot dpkg-deb --build wiringPi
   mv wiringPi.deb  wiringpi-`cat $here/VERSION`-1.deb