Support arm-unknown-linux-gnueabihf target

[gnzlbg]

arm-unknown-linux-gnueabihf and armv7-unknown-linux-gnueabihf don't seem to be currently supported

[malbarbo]

armv7-unknown-linux-gnueabihf is supported.

[gnzlbg]

@malbarbo indeed, I'll send a PR to support that one

[lytedev]

Any particular reason this hasn't been merged?

[gnzlbg]

@lytedev there is a PR: #158 but it takes too long to build and needs to be updated to a pre-built toolchain. Feel free to pick it up.