It looks like you are building for a musl target, but you have a GNU toolchain installed. You should either switch to a GNU target, or install a musl toolchain like this one.
Making progress. Now I'm getting an issue with compiling openssl. Here are some of the error messages:
/Users/X/target/arm-unknown-linux-musleabihf/debug/build/openssl-sys-0856812646163a02/out/openssl-build/build/src/ssl/d1_lib.c:439: undefined reference to `__gettimeofday_time64'
/usr/local/Cellar/musl-cross/0.9.9/libexec/bin/../lib/gcc/arm-linux-musleabihf/9.2.0/../../../../arm-linux-musleabihf/bin/ld: /Users/X/target/arm-unknown-linux-musleabihf/debug/build/openssl-sys-0856812646163a02/out/openssl-build/build/src/ssl/d1_lib.c:439: undefined reference to `__gettimeofday_time64'
collect2: error: ld returned 1 exit status
Not an ideal solution but I've decided to avoid using a dependency that relies on openssl since there have been numerous posts saying it's difficult to work with. I'm now able to compile everything.
If anyone knows how to get openssl compiling to work, that'd be awesome!