[PING 2][PATCH v3] Add pretty printers for the NPTL lock types

[Martin Galvan]

I went a bit deeper and I think the issue is that I'm adding the test
programs to 'test-srcs', which compiles them including libc-symbols.h.
I added them to test-srcs to make sure that even if we don't run the
test scripts, the test programs would be compiled.

The workaround would be adding a new target which compiled the test
programs by hand, like this:

$(tests-pretty-printers-out): $(objpfx)%.out: %.c
    $(CC) $(CFLAGS) -o $@ $*.c

That way, we could make tests-pretty-printers-out be a prerequisite of
the test target, which would run the python scripts only if requested
by run-built-tests.

I'm not sure if this is the cleanest way to do it, tough.
Additionally, I'd still need to know how to link against libpthread.
I'd appreciate it if anyone could give me a hand on how to write the
Makefile.