git-credential-netrc: use in-tree Git.pm for tests

The netrc test.pl script calls git-credential-netrc which imports the
Git module.  Pass GITPERLLIB to git-credential-netrc via PERL5LIB to
ensure the in-tree Git module is used for testing.

Signed-off-by: Luis Marsano <luis.marsano@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/credential/netrc/t-git-credential-netrc.sh

@@ -23,9 +23,10 @@
 	# The external test will outputs its own plan
 	test_external_has_tap=1
 
+	export PERL5LIB="$GITPERLLIB"
 	test_external \
 		'git-credential-netrc' \
-		perl "$TEST_DIRECTORY"/../contrib/credential/netrc/test.pl
+		perl "$GIT_BUILD_DIR"/contrib/credential/netrc/test.pl
 
 	test_done
 )

contrib/credential/netrc/test.pl

@@ -1,5 +1,4 @@
 #!/usr/bin/perl
-use lib (split(/:/, $ENV{GITPERLLIB}));
 
 use warnings;
 use strict;