p7519: fix watchman watch-list test on Windows

Only use the final portion of the test trash directory file name
when verifying that Watchman was started.

On Windows and under the SDK, $GIT_WORKTREE is a cygwin-style
path with forward slashes and a "/c/" drive name.  However
`watchman watch-list` reports a proper Windows-style pathname
with drive letters and backslashes.  This causes the grep to
fail.  Since we don't really care about the full pathname (and
we really don't want to bother with normalizaing them), just see
if the test-name portion of the path is found.

Signed-off-by: Jeff Hostetler <[email protected]>
Reviewed-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jeffhostetler

t/perf/p7519-fsmonitor.sh

@@ -101,7 +101,7 @@ test_expect_success "one time repo setup" '
 	# If Watchman exists, watch the work tree and attempt a query.
 	if test_have_prereq WATCHMAN; then
 		watchman watch "$GIT_WORK_TREE" &&
-		watchman watch-list | grep -q -F "$GIT_WORK_TREE"
+		watchman watch-list | grep -q -F "p7519-fsmonitor"
 	fi
 '