build: Add detection of little-endian ARM on Linux.

People compiling on ARM on Linux would have experienced problems
if they did not specify --profile. Problem reported by
Christopher Meng <cickumqt@gmail>.
build: Drop quotes from ARM targets.

What I get for speed commits...incompetent commits.
build: For now, my test systems are only armv{6,7}l.

Constrict to these targets.
build/arm: Specify -marm since some toolchains default to Thumb 2 still.

Thanks to Travis Geiselbrecht <geist@foobox> and John Hodge <acessdev@gmail>.
ck_pr/arm: Implement support for Thumb 2.

Patch submitted by Olivier Houchard <cognet@freebsd>.