Build the trillian_log_server and trillian_log_signer binary without depending on glibc

[roger2hk]

This PR avoids similar issue like google/certificate-transparency-go#1118.

Here is the distroless Dockerfile example for Go.
https://github.com/GoogleContainerTools/distroless/blob/main/examples/go/Dockerfile

Checklist

• I have updated the CHANGELOG.
• I have updated documentation accordingly (including the feature implementation matrix).

[mhutchinson]

Have you tried these images to confirm they work without cgo? I know that there are some libraries (e.g. sqlite, which is not relevant here) that require cgo. I'm not sure if others do?

[roger2hk]

Have you tried these images to confirm they work without cgo? I know that there are some libraries (e.g. sqlite, which is not relevant here) that require cgo. I'm not sure if others do?

Thanks for the reminder. I've revisited this issue and found out GoogleContainerTools/distroless#1342, which is an open issue related to the Debian version compatibility.