limit codegen-units to get the maximum optimization

[sabify]

Hello,

There might be a performance regression due to enabling lto without limiting the number of code generation units (codegen-units = 1).

References:
rust-lang/rust#47745
https://doc.rust-lang.org/rustc/codegen-options/index.html#codegen-units

[xgreenx]

codegen-units is 1 by default for release contract, so it is enabled.

[ascjones]

@xgreenx is right, it is already set by cargo-contract

[sabify]

If the ink is solely dependent on cargo-contract, how about removing the whole release profile block to avoid misconceptions?

[ascjones]

Yes we should do that since the profile for the ink workspace itself is not used when building a contract.