[binutils-gdb/gdb-8.0-branch] Make sure malloc is linked into gdb.cp/oranking.cc.

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT c2449d01b73b19acaf5add85b64c584fca9da366 ***

Author: Keith Seitz <keiths@redhat.com>
Branch: gdb-8.0-branch
Commit: c2449d01b73b19acaf5add85b64c584fca9da366

Make sure malloc is linked into gdb.cp/oranking.cc.

On some platforms, e.g., arm-eabi-none, we need to make certain that
malloc is linked into the program because the test suite uses function
calls requiring malloc:

(gdb) p foo101("abc")
evaluation of this expression requires the program to have a function "malloc".

gdb/testsuite/ChangeLog

	* gdb.cp/oranking.cc (dummy): New function to grab malloc.
	(main): Call it.