build-sys: always create the output directory first
$(MKDIR_P) is added where missing, and rules are standardized on one form of $(MKDIR_P), to make it easier to spot when it is missing. Single line $(MKDIR)&&command form is broken into two line form. https://bugs.freedesktop.org/show_bug.cgi?id=49459 For compilation in a separate build directory to work, when a file is generated, the rule must include an explicit mkdir first, unless the file is created at the top level. Even when building in a separate build-dir, automake would normally create all directories as a side result of creating the dependencies files. Therefore the bug was only visible with -C (turning off dependency generation).
Showing with 30 additions and 27 deletions