cmake: Skip libc & libusb version checks when cross-compiling

These checks break cross-compilation, as they require code to be
run on the host machine.
libbladeRF: Added additional elaboration to SC16Q11 format
libbladeRF: [WIP] Began adding RX timestamp support (untested)
libbladeRF/test: Moved PRNG routine to common dir for use in other tests
libbladeRF: [WIP] Added preliminary timestamps test
libbladeRF: [WIP] Added GPIO bit definitions for timestamps
libbladeRF: [WIP] Added missing cases to switch statements
libbladeRF: [WIP] Added GPIO setup to sync_init
libbladeRF/test: [WIP] Fixed bugs in timestamp test
libbladeRF: [WIP] Fixes to logic errors in RX metadata handling
libbladeRF: [WIP] Added missing reset of message number
libbladeRF/test: Fixed logical errors with random gap in timestamp test
libbladeRF/test: [WIP] Moved sync config to main app param setup
libbladeRF/test: [WIP] Fixed logic when seeking across buffers, misc fixes
libbladeRF/test: [WIP] Fixed calculation of metadata samples left in buffer
libbladeRF/test: [WIP] Added missing message number reset
libbladeRF/test: [WIP] Added more test cases to test_rx_scheduled
libbladeRF: Added API definition for FPGA counter mode enable bit
libbladeRF/test: [WIP] Added counter mode usage -- still debugging
libbladeRF[WIP]: Fixed copying of RX data to user buffer