I am compiling a new system and libusb-0.1.11 refuses to compile. I did a search and found a redhat site with a patch that works (with a bit of help). Included are the ebuild and patch files.
Created attachment 104614 [details] libusb-0.1.11.ebuild
Created attachment 104615 [details, diff] libusb-0.1.11-format.patch
Well, you didn't post any errors so hard to guess how it doesn't compile. Reopen if 0.1.12 still doesn't compile and needs this patch.