libusb1: Link with latomic only if compiler has no atomic builtins

This makes build use compiler to decide from where to get atomics
instead of assuming that it should always come from libatomic, helps
sharing build artifacts with OSes which may not have libatomic installed
because it is not required on those hosts.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>