Default v8 was fixed at 3.30.33, so running nix-build nixpkgs -A v8
would give us version 3.30.33, whereas nix-env -i v8 would install
version 4.5.107. Now, both commands build 4.5.107, and there is still an
option to install version 3.30.33
Similar to #14272, but fixes 4.5 build rather than generic.
- Ignores errors due to strict-overflow warnings
- Strips clang-only '-Wno-format-pedantic' flag out since this build
uses gcc
