t5562: fix perl path

Some systems do not have perl installed to /usr/bin. Use the variable
from the build settiings, and call perl directly than via shebang.

Signed-off-by: Max Kirillov <max@max630.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5562-http-backend-content-length.sh

@@ -31,6 +31,7 @@ test_http_env() {
 		PATH_TRANSLATED="$PWD/.git/git-$handler_type-pack" \
 		GIT_HTTP_EXPORT_ALL=TRUE \
 		REQUEST_METHOD=POST \
+		"$PERL_PATH" \
 		"$TEST_DIRECTORY"/t5562/invoke-with-content-length.pl \
 		    "$request_body" git http-backend >act.out 2>act.err
 }

t/t5562/invoke-with-content-length.pl

-#!/usr/bin/perl
 use 5.008;
 use strict;
 use warnings;