Accelerate `cargo cross` builds

[jssblck]

Important

This is about cargo cross, not cross, which is a distinct project. Of course.

In #124, we stopped failing to build builds that use cargo cross.
However, builds that use cargo cross are not accelerated:

; cargo clean && hurry-dev cargo cross build -p hurry
     Removed 5261 files, 1.7GiB total
No target specified, using host: aarch64-apple-darwin
Execution configuration:
  Command: build
  Source directory: /Users/jess/projects/hurry
  Package: hurry
  Profile: release
  Targets: aarch64-apple-darwin
[1/1] Processing target: aarch64-apple-darwin
--------------------------------------------------------------------------------
Executing build for aarch64-apple-darwin...
Using system default linker for aarch64-apple-darwin
Environment variables:
  CARGO_UNSTABLE_HOST_CONFIG=true
  CARGO_UNSTABLE_TARGET_APPLIES_TO_HOST=true
  CARGO_TARGET_APPLIES_TO_HOST=false
Run command:
  cargo build --target aarch64-apple-darwin --release --package hurry
   Compiling proc-macro2 v1.0.101
   Compiling unicode-ident v1.0.19
   ...
   Compiling reqwest v0.12.24
   Compiling clients v0.0.0 (/Users/jess/projects/hurry/packages/clients)
   Compiling hurry v0.0.0 (/Users/jess/projects/hurry/packages/hurry)
    Finished `release` profile [optimized] target(s) in 26.48s
Build successful: aarch64-apple-darwin (took 26s)
--------------------------------------------------------------------------------
All build operations completed successfully!
Total time: 26s

This is because we simply passthrough commands with cargo cross and don't have a special case handler for cargo cross build like we do for cargo build. Note that we also need to fix #177 first, because cargo cross always builds with --target specified.

[jssblck]

Resolved by #254

Incorrect: 254 implemented support for cross, not cargo cross, oops. Reopening.