gdb-7.6: fix cygwin check in configure script

This is a fix which avoids false positives if the search pattern
"lose" is found in path descriptions in comments generated by the
preprocessor we hit in our development environment.

[gdb Bug #16152] -- https://sourceware.org/bugzilla/show_bug.cgi?id=16152

Upstream-Status: Accepted
Signed-off-by: Steffen Sledz <sledz@dresearch-fe.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>