t9700-perl-git.sh: Fix a test failure on Cygwin

The t/t9700/test.pl script uses method invocation syntax when
using the Cwd module to determine the current working directory.
This fails on cygwin, since cygwin perl specifically checks for
any arguments to the cwd() function and croak()'s with the message
"Usage: Cwd::cwd()". (In perl v5.8.8 distribution, see the file
perl-5.8.8/cygwin/cygwin.c lines 139-157)

In order to avoid the problem, we replace the method invocation
syntax with a simple function call.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9700/test.pl

@@ -13,7 +13,7 @@
 BEGIN { use_ok('Git') }
 
 # set up
-our $abs_repo_dir = Cwd->cwd;
+our $abs_repo_dir = cwd();
 ok(our $r = Git->repository(Directory => "."), "open repository");
 
 # config