What steps will reproduce the problem?

./configure --target=iphone --with-gcc-version=4.2.1 --with-sdk-version=5.0 --with-developer-path=path=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer

What is the expected output? What do you see instead?

./configure: line 4364: syntax error near unexpected token LIBUSB,' ./configure: line 4364: PKG_CHECK_MODULES(LIBUSB, libusb-1.0, HAVE_LIBUSB="yes", HAVE_LIBUSB="no")'

That goes away if you install libusb.