Closes#993.
We do not need to descend into the modules to know what to do on
`make clean BOARD=blub`. We can just invoke `rm -rf bin/blub`.
This PR only keeps the descending into the USEPKGs, since they might
want to delete cached/downloaded/extracted data.
Application developers use `$(USEMODULES)` in their Makefiles to have
the relevant functionally automagically added to their apps. This even
does basic dependency tracking by means of `Makefile.dep`.
But an important thing is missing: the automatic adding of include
paths. This is inconvenient, error prone, and will hinder the RIOT core
developers in future to change folder structures.
In #664 I added a test that determines if the supplied compiler
understands the `-fno-delete-null-pointer-checks` flag. The problem is
that the `$(CC)` supplied on command line or in the application's
Makefile is used, but not the one the `$(BOARD)`'s Makefile sets.
That problem was overlooked as all the boards use GCC, and GCC happens
to know the flag. But if some future board does not use GCC, then the
wrong order of the checks could pose a problem.
An application might want to use C11 features. The user would assume
that setting `CFLAGS=-std=gnu11` in the Makefile would work. It does not
since the board's Makefile.include shadows the `-std` flag.
This patch removes the `-std=gnu99` from the various Makefile.includes,
and sets the flag in the common Makefile.include of RIOT instead.
If an `-std` flag was provided by an earlier Makefile (the application,
the board, or the CPU [whilst only the former one should]), then no
additional flag is set. It is first tested if the supplied compiler
understands `-std=gnu99`, then `-std=c99`.
Currently pkg/USING says one should use
`EXTERNAL+=$(RIOTBASE)/pkg/<pkg_name>` to enable PKG modules.
Using this line the PKG will be compiled but not linked.
This change adds a USEPKG variable to be used like
`USEPKG += <pkg_name>`, which looks less clumsy and gets the PKG linked
in the binary.
* add missing $(AD) to osx $(LINK) invocation
* move osx build determination to native makefile
* move old libc test to native makefile
* set objcopy to "true" - it is superfluous for native no matter what the system is
* add some documentation to natives makefile
