Display a more user-friendly error when compiling on Linux/arm64

[rtyler]

Without this change, users may be greeted with the following confusing
message when trying to build on Linux/arm64

error[E0601]: `main` function not found in crate `sccache_dist`
   --> /home/ubuntu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/sccache-0.10.0/src/bin/sccache-dist/main.rs:835:2
    |
835 | }
    |  ^ consider adding a `main` function to `/home/ubuntu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/sccache-0.10.0/src/bin/sccache-dist/main.rs`

For more information about this error, try `rustc --explain E0601`.

With this change:

error: Distributed compilation is only support on Linux/x86_64 and FreeBSD!
  --> src/bin/sccache-dist/main.rs:43:5
   |
43 |     compile_error!("Distributed compilation is only support on Linux/x86_64 and FreeBSD!");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.94%. Comparing base (36c8b89) to head (b4c7e06).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2435      +/-   ##
==========================================
+ Coverage   67.31%   70.94%   +3.63%     
==========================================
  Files          64       65       +1     
  Lines       35165    35523     +358     
==========================================
+ Hits        23670    25203    +1533     
+ Misses      11495    10320    -1175     

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[sylvestre]

thanks