Rust

Make bon builders optional #1168

Job	Run time
build_bin_spec (nightly)	1m 10s
build_lib_test (nightly)	1m 7s
build_bin_spec (beta)	1m 24s
build_lib_test (beta)	1m 22s
build_bin_spec (stable)	1m 16s
build_wasm (nightly)	48s
clippy_format	1m 56s
build_lib_test (stable)	1m 33s
build_bin_spec ($MSRV)	2m 23s
build_wasm (beta)	49s
build_lib_test ($MSRV)	2m 53s
build_wasm (stable)	43s
lockfile	2m 36s
build_wasm ($MSRV)	1m 59s
no_features_build_test (nightly)	27s
no_features_build_test (beta)	27s
no_features_build_test (stable)	41s
no_features_build_test ($MSRV)	42s
	24m 16s

Provide feedback