main/musl: add conflict against glibc
There is a third-party package which installs glibc in an allegedly compatible way with musl. It is our opinion that while this package can co-exist with musl, the end result of running binary blobs that combine libraries expecting musl libc with glibc code, without a proper emulation layer like gcompat, results in undefined behavior.
Accordingly, we are unwilling to provide support for this configuration. This has been our historic position on the alpine-pkg-glibc project since its inception, however, due to increased attention and attempts to use it in production, we feel it appropriate to signal our position more forcefully.