Please add an ARMv7 build to releases

[jwlsinx]

While trying to use on a new device, I get the following error

$ ./dnscrypt-proxy -version
runtime: this system has multiple CPUs and must use
atomic synchronization instructions. Recompile using GOARM=7.

This appears to be an issue not covered during the discussion in #682

[jwlsinx]

Realized that this is exactly what was raised in #682 but not fully resolved. I will build manually for now.

[jedisct1]

Does it work with GOARM=6?

[jwlsinx]

Does it work with GOARM=6?

No, I get the same error.

[jedisct1]

GOARM=7?

[jwlsinx]

Building with GOOS=freebsd GOARCH=arm GOARM=7 go build -ldflags="-s -w" works (pulled from #682).

The GOOS=freebsd GOARCH=arm GOARM=6 go build -ldflags="-s -w" build failed though (same error on device).