Strip target suffix for cargo-zigbuild compatibility

[bet4it]

When using cargo-zigbuild, target triples may include additional suffixes like glibc versions (e.g. aarch64-unknown-linux-gnu.2.17). This change strips any suffix after the dot to ensure compatibility with rustc, which only accepts standard target triples.

[davidhewitt]

@messense does this seem correct to you? Seems to me like cargo-zigbuild might be passing the wrong information down rather than applying a patch here? 🤔