Adjust gdb.base/bp-cond-failure.exp for Cygwin

Adjust gdb.base/bp-cond-failure.exp for Cygwin

Currently on Cygwin, I get:

 Running /home/alves/gdb/src/gdb/testsuite/gdb.base/bp-cond-failure.exp ...
 FAIL: gdb.base/bp-cond-failure.exp: access_type=char: cond_eval=auto: multi-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=char: cond_eval=auto: single-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=short: cond_eval=auto: multi-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=short: cond_eval=auto: single-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=int: cond_eval=auto: multi-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=int: cond_eval=auto: single-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=long long: cond_eval=auto: multi-loc: continue
 FAIL: gdb.base/bp-cond-failure.exp: access_type=long long: cond_eval=auto: single-loc: continue

On GNU/Linux, we see:

 Breakpoint 2.1, foo () at .../src/gdb/testsuite/gdb.base/bp-cond-failure.c:21
 21        return 0;     /* Multi-location breakpoint here.  */
 (gdb) PASS: gdb.base/bp-cond-failure.exp: access_type=char: cond_eval=auto: multi-loc: continue

While on Cygwin, we see:

 Thread 1 "bp-cond-failure" hit Breakpoint 2.1, foo () at .../src/gdb/testsuite/gdb.base/bp-cond-failure.c:21
 21        return 0;     /* Multi-location breakpoint here.  */
 (gdb) FAIL: gdb.base/bp-cond-failure.exp: access_type=char: cond_eval=auto: multi-loc: continue

The difference is the "Thread 1" part in the beginning of the quoted
output.  It appears on Cygwin, but not on Linux.  That's because on
Cygwin, all inferiors are multi-threaded, because both Windows and the
Cygwin runtime spawn a few helper threads.

Fix this by adjusting the gdb.base/bp-cond-failure.exp testcase to
work with either single- or multi-threaded inferiors.

The testcase passes cleanly for me after this.

Approved-by: Kevin Buettner <kevinb@redhat.com>
Change-Id: I5ff11d06ac1748d044cef025f1e78b8f84ad3349