Cargo contract does not obey target-dir setting in Cargo.toml

[goastler]

Describe the bug
Cargo contract does not obey target-dir setting in Cargo.toml. It defaults to the ./target directory relative to the src files

To Reproduce
Steps to reproduce the behavior:

1. clone flipper contract
2. add

[build]
target-dir = '/path/to/my/non/default/target/dir'

to the Cargo.toml
3. run `cargo contract build`
4. observe that the build artifacts end up in the default `./target` dir, not the one set in Cargo.toml

**Expected behavior**
The build output to be put in the specified target directory

**Environment (please complete the following information):**
 - OS: Ubuntu 22.04.3 LTS
 - `cargo-contract` version [e.g. 3.0.1] cargo-contract-contract 3.0.1-unknown-x86_64-unknown-linux-gnu
 - ink! version: [e.g. 4.2.0] 4.3.0
 - `substrate-contracts-node` version: [e.g. 0.14.0] 0.30.0