metaeuk: fix missing <cstdint> under GCC 14

[gonzabotmdp]

Summary

Same class of bug as in spades (same root cause, unrelated codebase -- both packages independently hit this): metaeuk vendors mmseqs2 under lib/mmseqs, and its C++ sources use fixed-width int types (uint32_t/uint64_t/...) throughout while relying on getting <cstdint> transitively from whatever standard header happened to pull it in on older GCC. GCC 14's libstdc++ doesn't, so the build fails, e.g.:

lib/mmseqs/src/commons/Util.h:87:12: error: 'uint64_t' does not name a type
lib/mmseqs/src/prefiltering/Indexer.h:125:9: error: 'uint64_t' was not declared in this scope

A static scan found 47 affected files. Rather than patch each one (and risk missing a 48th), force the header into every translation unit at the compiler level: -include cstdint for C++ sources, -include stdint.h for C sources (the plain C compiler doesn't see the C++ wrapper header).

Testing

Installed metaeuk@6-a5d39d9 with %gcc@14.2.0 as a dependency of busco@6.1.0, confirmed it builds clean and busco runs a real gene-prediction pipeline end to end using it.