Replace cli flag `--prebuilt-platform` with `--build-host` #2243

Job	Run time
check-changes	18s
ran-none	0s
start-nix-linux-x86-64-tests / nix-linux-x86	35m 59s
start-nix-linux-aarch64-build-default-test / nix-linux-arm64	18s
start-macos-x86-64-tests / test-rust-macos-x86-64	31m 43s
start-nix-linux-aarch64-cargo-build-test / nix-linux-arm64	43m 21s
start-nix-macos-apple-silicon-tests / nix-apple-silicon	38m 25s
start-roc-benchmarks / benchmark roc programs	17m 7s
start-ubuntu-x86-64-nix-tests-debug / cargo test debug nix	18m 26s
start-ubuntu-x86-64-tests / test zig, rust, wasm...	28m 29s
start-windows-release-build-test / windows-release-build	12m 26s
start-windows-tests / windows-test-subset	24m 24s
ran-full	0s
finish	1s
	4h 10m 57s

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