Merge #20880: gitian: Use custom MacOS code signing tool
2c403279e2f0f7c8c27c56d4e7b0573c59571f0a gitian: Remove codesign_allocate and pagestuff from MacOS build (Andrew Chow)
f55eed251488d70d5e2e3a2965a4f8ec0c476853 gitian: use signapple to create the MacOS code signature (Andrew Chow)
95b06d21852b28712db6c710e420a58bdc1a0944 gitian: use signapple to apply the MacOS code signature (Andrew Chow)
42bb1ea363286b088257cabccb686ef1887c1d3b gitian: install signapple in gitian-osx-signer.yml (Andrew Chow)
Pull request description:
The MacOS code signing issues that were encountered during the 0.21.0 release cycle have shown that it is necessary for us to use a code signing tool for which the source code is available and modifiable by us. Given that there appears to not be such a tool available, I have written such a tool, [signapple](https://github.com/achow101/signapple), that we can use. This tool is able to create a valid MacOS code signature, detach it in a way that we were doing previously, and attach it to the unsigned binary. This tool can also verify that the signature is correct.
This PR implements the usage of that tool in the gitian build for the code signed MacOS binary. The code signer will use this tool to create the detached signature. Gitian builders will use this tool to apply the detached signature. The `gitian-osx-signer.yml` descriptor has been modified to install this tool so that the `detached-sig-apply.sh` script can use it. Additionally, the `codesign_allocate` and `pagestuff` tools are no longer necessary so they are no longer added to the tarball used in code signing. Lastly, both the `detached-sig-create.sh` and `detached-sig-apply.sh` scripts are made to be significantly less complex and to not do unexpected things such as unpacking an already unpacked tarball.
The detached code signature that signapple creates is almost identical to that which we were previously creating. The only difference is that the cpu architecture name is included in the extension (e.g. we have `bitcoin-qt.x86_64sign` instead of `bitcoin-qt.sign`). This was done in order to support signing universal binaries which we may want to do in the future. However signapple can still apply existing code signatures as it will accept the `.sign` extension. If it is desired, it can be modified to produce signatures with just the `.sign` extension. However I do not think it is necessary to maintain compatibility with the old process.
ACKs for top commit:
Code review ACK 2c403279e2f0f7c8c27c56d4e7b0573c59571f0a