gdb/testsuite: make pie-execl.exp work with native-gdbserver

This test passes the path of an executable to execute as argv[1] to the
inferior.  This test is currently skipped with remote targets (e.g.
native-gdbserver), because it previously wasn't possible to pass
arguments to inferiors on such targets in the testsuite.  Remove that
check, and use the new -inferior-args runto option to pass the args to
the inferior.

Add

  require {!target_info exists noargs}

to reflect that the test relies on inferior args.

Change-Id: If3b884421b453d6ca93c19ca13314bbb7869218c
Reviewed-By: Tankut Baris Aktemur <TankutBaris.Aktemur@amd.com>