libxml2: fix makefile for ptests
Changes to Makefile in latest version mean when "make -k runtests" is executed,
it leads to errors like:
| make: *** No rule to make target 'runtest.c', needed by 'runtest.o'.
| make: *** No rule to make target 'SAX.c', needed by 'SAX.lo'.
| make: *** No rule to make target 'entities.c', needed by 'entities.lo'.
| make: *** No rule to make target 'encoding.c', needed by 'encoding.lo'.
Make sure that we don't try to check and compile the tests again on the target.
(From OE-Core rev:
5cf92ca436e1a1ba60fec8b30b6cb3cfd4842bc8)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
