Cleanup metadata codegen slightly (#903)

21 jobs for master in 7 minutes and 39 seconds (queued for 4 seconds)
Name Stage Failure
failed
clippy-wasm Workspace
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= note: `-D unused-unsafe` implied by `-D warnings`

error: could not compile `ink_env` due to previous error

Caused by:
process didn't exit successfully: `sccache /usr/local/rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/clippy-driver rustc --crate-name ink_env --edition=2018 crates/env/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata -C embed-bitcode=no -C debuginfo=2 -C metadata=723d281c2579fc82 -C extra-filename=-723d281c2579fc82 --out-dir /ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps --target wasm32-unknown-unknown -L dependency=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps -L dependency=/ci-cache/ink/targets/master/clippy-wasm/debug/deps --extern arrayref=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libarrayref-7ca543c11df82a23.rmeta --extern cfg_if=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libcfg_if-152302b13a9219ee.rmeta --extern derive_more=/ci-cache/ink/targets/master/clippy-wasm/debug/deps/libderive_more-edf18f57ac540f89.so --extern ink_allocator=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libink_allocator-a4507f5519d8510e.rmeta --extern ink_prelude=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libink_prelude-3f704995c45f81cd.rmeta --extern ink_primitives=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libink_primitives-287ce091e5c47ae3.rmeta --extern num_traits=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libnum_traits-6109f0b5c882ae0e.rmeta --extern scale=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libparity_scale_codec-a032c486482c3792.rmeta --extern paste=/ci-cache/ink/targets/master/clippy-wasm/debug/deps/libpaste-1d007800db85bb25.so --extern sp_arithmetic=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libsp_arithmetic-4a09037da21b6c0c.rmeta --extern static_assertions=/ci-cache/ink/targets/master/clippy-wasm/wasm32-unknown-unknown/debug/deps/libstatic_assertions-a8388fa09641602e.rmeta` (exit status: 1)
Cleaning up file based variables
ERROR: Job failed: exit code 1