Make gdb.base/foll-exec.exp test pattern more general

Make gdb.base/foll-exec.exp test pattern more general

Testing a powerpc toolchain running gdbserver on the other end i noticed a
failure in gdb.base/foll-exec.exp.  Turns out gdb is outputting a slightly
different pattern due to the presence of debug information.

--
foll-exec is about to execlp(execd-prog)...^M
Continuing.^M
process 21222 is executing new program: gdb.d/outputs/gdb.base/foll-exec/execd-prog^M
^M
Catchpoint 2 (exec'd gdb.d/outputs/gdb.base/foll-exec/execd-prog), _start () at ../sysdeps/powerpc/powerpc32/dl-start.S:32^M
--

Notice the presence of source file information.

Now, on my local machine, i get this:

--
foll-exec is about to execlp(execd-prog)...^M
Continuing.^M
process 9285 is executing new program: gdb/testsuite/outputs/gdb.base/foll-exec/execd-prog^M
^M
Catchpoint 2 (exec'd gdb/testsuite/outputs/gdb.base/foll-exec/execd-prog), 0x00007ffff7dd7cc0 in ?? () from /lib64/ld-linux-x86-64.so.2^M
--

So the output differs slightly and the testcase is actually expecting only
the second form with the "in" anchor.

This patch removes the "in" pattern and lets the test match both kinds of
output.

gdb/testsuite/ChangeLog:

2016-10-28  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.base/foll-exec.exp (do_exec_tests): Make test pattern more
	general.