Add support for arm-linux-musleabihf

[j8r]

Follow up of #5862.
All credits go to @jirutka .

Resolves #5467

[RX14]

is it tested?

[ysbaddaden]

The original PR was as good as the arm-linux-gnueabi target, which means that it had the exact same hard/soft float issues on the same hardware. I couldn't test it better because I miss an armv7 Alpine image that I can just run in qemu (I use Raspbian for glibc).

[j8r]

I got this errors when cross compiling with a newly compiled compiler:

export  LLVM_CONFIG=/usr/bin/llvm5-config
make FLAGS="--target arm-linux-musleabihf --link-flags=-no-pie --verbose"

...
/usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: _main.o: relocations in generic ELF (EM: 40)
/usr/lib/gcc/x86_64-alpine-linux-musl/8.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: _main.o: error adding symbols: file in wrong format

[j8r]

I would like to go forward on this, but struggling with cross-compilation 😕

[flying-sausages]

Bump?