Detailed description

• Not a feature.
• The problem is BMDA fails to build from source (FTBFS) on FreeBSD because of no <alloca.h> and missing hidapi-hidraw.
• PR solves this by purging all (3) of alloca.h references in light of Msvc fixes #1661 and guarding the remaining inclusion by OS-specific macro. And adding a proper/available hidapi library name.

Tested on NomadBSD 13.2-RELEASE and a bunch of cheap adapters I have. HOSTED_BMP_ONLY=0. CMSIS-DAP (Picoprobe, free-dap) are detected, opened in v2/bulk mode and result in successful scan of an empty chain (nothing wired up). BMP-compatibles work only after indicating a --device /dev/ttyU0 and under root privileges (there is no /dev/serial/by-id); including scanning SWD and attaching to a Cortex-M target. JLink and STLink/v2 result in a crash in libusb.so.3.0.0 due to write into zero page on first bulk write transaction. ASAN=1 also works btw. FTDI MPSSE not tested. Noting that devel/openocd-0.11.0 works on the same machine with the same JLink/STLink without crashing, and devel/gdb looks like built with multiarch support.

Building: sudo pkg install libftdi1 hidapi and then gmake -C src/ PROBE_HOST=hosted HOSTED_BMP_ONLY=0 CC=gcc12 -j6 because Makefiles of this project are incompatible with default bmake to which make aliases.
This PR does not cover building BMF and libopencm3 under *BSD. I could not install https://www.freshports.org/devel/gcc-arm-embedded/ due to symlink collisions, but python 3.9 is present (for GENHDR) and there may not be other problems to that.

Your checklist for this pull request

• I've read the Code of Conduct
• I've read the guidelines for contributing to this repository
• It builds for hardware native (make PROBE_HOST=native)
• It builds as BMDA (make PROBE_HOST=hosted)
• I've tested it to the best of my ability
• My commit messages provide a useful short description of what the commits do

Closing issues

@DanielO may try using BMDA on his FreeBSD machine now, in addition to the Orbuculum suite (see orbcode/orbuculum#134)