gdb/testsuite/rocm: fix rocm-multi-inferior-gpu.cpp The gdb/testsuite/gdb.rocm/multi-inferior-gpu.cpp testcase contains a call to execl which does not have NULL as a last argument. This is an invalid use of execl. This patch fixes this oversight. Change-Id: I03b60abe30468d71ba5089b240c6d00f9b8883b2 Approved-By: Tom Tromey <tom@tromey.com>