Internal headers (`crypto`, `internal` and `prov`) in `zig-out/include`

Hi,
I'm new to Zig (2 days now) and I'm working on making https://github.com/kubernetes-client/c/ working with Zig as I'd like to rewrite some of my scripts into Zig as learning projects.

But the library depends on OpenSSL and it imports it in its public header files so when not using system's OpenSSL I do

```zig
b.installArtifact(openssl_lib);
```

so that the library is distributed in a working state when using vendored OpenSSL.

However the OpenSSL library installs some internal include directories, as far as I understand, which I don't think should be installed.

```
zig-out/include/
├── crypto
├── curl
├── internal
├── kubernetes
├── openssl
└── prov

7 directories, 0 files
```

The directories have some generic names and as far as my research goes these headers are internal and upstream only exports the `openssl` directory

```
/nix/store/dy64cxaygvmjfznysgxk501yds8jij6s-openssl-3.6.1-dev/include
└── openssl

2 directories
```

So is there a reason why

https://github.com/allyourcodebase/openssl/blob/6b318b447c8ff7529e3a2337a1df2a9b4816fee2/build.zig#L1255

isn't

```zig
lib.installHeadersDirectory(b.path("include/openssl"), "openssl", .{});
```

I'm opening an issue and not a PR as I'm not sure whether I'm missing something. If there are no requirements for those extra directories to be installed I'll gladly open a PR to make that change.