Fix include paths on Linux (from bartbes)

--HG--
branch : box2d-update

platform/unix/gen-makefile

@@ -3,8 +3,8 @@ echo Generating src/Makefile.am ...
 cd src
 inc_current=.
 inc_modules="$inc_current/modules"
-inc_box2d="$inc_current/libraries/Box2D"
-echo "AM_CPPFLAGS = -I$inc_current -I$inc_modules -I$inc_box2d -I/usr/include/AL -I/usr/include/freetype2  \$(INCLUDE_LUA) -I/usr/include/SDL \$(FILE_OFFSET)
+inc_libraries="$inc_current/libraries"
+echo "AM_CPPFLAGS = -I$inc_current -I$inc_modules -I$inc_libraries -I/usr/include/AL -I/usr/include/freetype2  \$(INCLUDE_LUA) -I/usr/include/SDL \$(FILE_OFFSET)
 AUTOMAKE_OPTIONS = subdir-objects
 DEFAULT_INCLUDES =
 SUBDIRS =