cmake: fix lua_source for files stored in superproject

If Tarantool is built as a subproject, and there's a Lua source file
stored in the superproject directory, its path won't start with
PROJECT_SOURCE_DIR and hence won't be replaced with PROJECT_BINARY_DIR
by the lua_source() function. As a result, the lua.c file generated by
lua_source() will be put in the source directory instead of the binary
directory. Fix this by using CMAKE dirs instead of PROJECT dirs.

Ironically, CMAKE dirs were replaced with PROJECT dirs everywhere in
the first place to allow building Tarantool as a subproject, see commit
d8097325 ("cmake: align folders dependencies"). This patch basically
reverts that change.

NO_DOC=cmake
NO_TEST=cmake
NO_CHANGELOG=cmake

cmake/utils.cmake

@@ -40,7 +40,7 @@ endmacro(set_source_files_compile_flags)
 # A helper function to compile *.lua source into *.lua.c sources
 function(lua_source varname filename symbolname)
     if (IS_ABSOLUTE "${filename}")
-            string (REPLACE "${PROJECT_SOURCE_DIR}" "${PROJECT_BINARY_DIR}"
+        string (REPLACE "${CMAKE_SOURCE_DIR}" "${CMAKE_BINARY_DIR}"
             genname "${filename}")
         set (srcfile "${filename}")
         set (tmpfile "${genname}.new.c")