Fix conditional compilation directive #1163

Job	Run time
Clippy	27s
cargo-c dynamic library	9s
Clippy (--no-default-features --features="c-allocator")	2m 36s
Build and test (stable, ubuntu-latest, x86_64-unknown-linux-gnu)	33s
QEMU build & test (stable, ubuntu-latest, s390x-unknown-linux-gnu, s390x-linux-gnu-gcc)	37s
Clippy (--no-default-features --features="rust-allocator")	25s
Build and test (msrv, ubuntu-latest, x86_64-unknown-linux-gnu)	43s
Build and test (beta, ubuntu-latest, x86_64-unknown-linux-gnu)	46s
QEMU build & test (stable, ubuntu-latest, i686-unknown-linux-gnu, i686-linux-gnu-gcc)	36s
Smoke-test fuzzing targets (default)	1m 40s
Build and test (stable, macos-latest, x86_64-apple-darwin)	42s
Build and test (stable, macos-14, aarch64-apple-darwin)	40s
Smoke-test fuzzing targets (c-allocator)	1m 32s
Smoke-test fuzzing targets (stable, macos-14, aarch64-apple-darwin)	2m 45s
Build and test (stable-x86_64-gnu, windows-2022, x86_64-pc-windows-gnu)	42s
Smoke-test fuzzing targets (rust-allocator)	1m 34s
vanilla dynamic library	15s
Miri	1m 44s
run flate2 test suite	21s
wasm32	27s
	19m 14s

Provide feedback