Do not strip CR when grepping HTTP headers.

By default, MSYS grep reads in text-mode and converts CRLF into LF line
endings. For testing HTTP use binary mode (-U) as checking is done for
CR in HTTP headers

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
diff --git a/t/test-lib.sh b/t/test-lib.sh
index a85e795..2af8f10 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -970,6 +970,7 @@
 	# no POSIX permissions
 	# backslashes in pathspec are converted to '/'
 	# exec does not inherit the PID
+	test_set_prereq MINGW
 	;;
 *)
 	test_set_prereq POSIXPERM