wasm-builder: Use riscv32emac-unknown-none-polkavm.json target #5505

Job	Run time
preflight / preflight	44s
preflight / ci-versions	1m 17s
test-frame-ui	2m 12s
test-full-crypto-feature	2m 12s
test-node-metrics	2m 12s
cargo-check-benches (master)	2m 11s
cargo-check-benches (current)	2m 13s
cargo-check-all-crate-macos	2m 45s
cargo-check-each-crate (1)	2m 11s
cargo-check-each-crate (2)	2m 10s
cargo-check-each-crate (3)	2m 12s
cargo-check-each-crate (4)	2m 10s
cargo-check-each-crate (5)	2m 12s
cargo-check-each-crate (6)	2m 11s
cargo-check-each-crate (7)	2m 10s
check-tracing	1s
test-frame-examples-compile-to-wasm	1s
check-metadata-hash	1s
node-bench-regression-guard	1s
test-deterministic-wasm	1s
All test misc tests passed	1s
	31m 8s

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