Suggestions put explicit paths into the config

[jayvdb]

I see a lot of cases like

lcms2-sys's build script emitted disallowed instruction `cargo:include=/home/jayvdb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/lcms2-sys-4.0.5/vendor/include`
1)  Allow build script for `lcms2-sys.build` to emit instruction `cargo:include=/home/jayvdb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/lcms2-sys-4.0.5/vendor/include`
2)  Allow build script for `lcms2-sys.build` to emit instruction `cargo:include=*`
3)  Allow build script for `lcms2-sys.build` to emit instruction `cargo:*`
dN) Diff for fix N. e.g 'd1'

and

libwebp-sys's build script emitted disallowed instruction `cargo:rustc-link-search=native=/home/jayvdb/work/rosalind/target/cackle/build/libwebp-sys-2e794fb2fca1ac0c/out`
1)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:rustc-link-search=native=/home/jayvdb/work/rosalind/target/cackle/build/libwebp-sys-2e794fb2fca1ac0c/out`
2)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:rustc-link-search=native=*`
3)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:rustc-link-search=*`
4)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:rustc-link-*`
5)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:rustc-*`
6)  Allow build script for `libwebp-sys.build` to emit instruction `cargo:*`
dN) Diff for fix N. e.g 'd1'

Option 1 is very unlikely what the user wants as it wont work for another user.