devel/corrade: fix build on aarch64, missing FreeBSD code

• add CPU detection code for armv7, aarch64 (armv7 is still broken for other reasons)
• add missing FreeBSD support code for executableLocation()
• hook up test suite

See also: https://github.com/mosra/corrade/issues/171
Approved by: yuri (maintainer)
Differential Revision: https://reviews.freebsd.org/D40202