devel/linux_libusb: disable date/time nonreproducible build warning

The base system build infrastructure will add -Wdate-time, to avoid
use of nonreproducible __DATE__ and __TIME__ in the base system.

This port makes use of a GCC that does not support -Wdate-time, so
opt out of the warning.

Reviewed by:	hselasky
Approved by:	jrm
PR:		267902 [exp-run]
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D37506