Add rules for libusb Makefile.am building on osx
diff --git a/compat/libusb-1.0/configure.ac b/compat/libusb-1.0/configure.ac
index c21c344..1fccea7 100644
--- a/compat/libusb-1.0/configure.ac
+++ b/compat/libusb-1.0/configure.ac
@@ -26,7 +26,7 @@ lt_revision="0"
lt_age="0"
LTLDFLAGS="-version-info ${lt_current}:${lt_revision}:${lt_age}"
-AM_INIT_AUTOMAKE
+AM_INIT_AUTOMAKE([foreign subdir-objects])
AM_MAINTAINER_MODE
AC_CONFIG_SRCDIR([libusb/core.c])