Add Snap build for armhf/armv7 architecture

[danielpgross]

Attempting to build the snap on Snapcraft Cloud for armhf produces the following error:

zig build --global-cache-dir /build/friendly-neighbor/parts/friendly-neighbor/build/zig-cache/
thread 9738 panic: integer overflow
/snap/zig/8738/lib/std/process.zig:1222:22: 0xb6a43 in totalSystemMemoryLinux (build)
    return kilobytes * 1024;
                     ^
/snap/zig/8738/lib/std/process.zig:1164:42: 0xa578b in totalSystemMemory (build)
            return totalSystemMemoryLinux() catch return error.UnknownTotalSystemMemory;
                                         ^
/snap/zig/8738/lib/build_runner.zig:316:48: 0xa1dcb in main (build)
        run.max_rss = process.totalSystemMemory() catch std.math.maxInt(usize);
                                               ^
/snap/zig/8738/lib/std/start.zig:370:37: 0x904e3 in posixCallMainAndExit (build)
            var i: usize = 0;
                                    ^
???:?:?: 0x0 in ??? (???)
error: the following build command crashed:
/build/friendly-neighbor/parts/friendly-neighbor/build/zig-cache/o/4fb5c8308bb66929791e1c0a7a99fb3b/build /snap/zig/8738/zig /build/friendly-neighbor/parts/friendly-neighbor/build /build/friendly-neighbor/parts/friendly-neighbor/build/zig-cache /build/friendly-neighbor/parts/friendly-neighbor/build/zig-cache/
'override-build' in part 'friendly-neighbor' failed with code 1.

Seems to be caused by ziglang/zig#17596.

We should ideally support armhf, since many low-power devices use it, including Raspberry Pi version 2 and earlier.

[CommanderTso]

Just ran into this trying to install on my Pi 3; I'd love to be able to use this on there. Thanks.