[BUILD] Current version `lib` symlinks showing up in build from previous version

I'm on Ubuntu 24.04. What I'm doing inside my cloned OIIO repo is:

```
git checkout v2.5.15.0
cmake -DOpenImageIO_BUILD_MISSING_DEPS=all -B build -S .
cmake --build build --target install
```

What I get in `dist/lib` is this:
```
drwxrwxr-x - moritz 9 Sep 15:32 cmake
lrwxrwxrwx - moritz 9 Sep 15:32 libOpenImageIO.so -> libOpenImageIO.so.2.6.4
.rw-r--r-- 14M moritz 3 Sep 13:20 libOpenImageIO.so.2.5.15
lrwxrwxrwx - moritz 9 Sep 15:32 libOpenImageIO.so.2.6.4 -> libOpenImageIO.so.2.5.15
lrwxrwxrwx - moritz 9 Sep 15:32 libOpenImageIO_Util.so -> libOpenImageIO_Util.so.2.6.4
.rw-r--r-- 1.2M moritz 3 Sep 13:15 libOpenImageIO_Util.so.2.5.15
lrwxrwxrwx - moritz 9 Sep 15:32 libOpenImageIO_Util.so.2.6.4 -> libOpenImageIO_Util.so.2.5.15
drwxrwxr-x - moritz 9 Sep 15:32 pkgconfig
drwxrwxr-x - moritz 9 Sep 15:32 python3.12
```

Is this expected? How does `v2.6.5` get in there?

Reproduce the report by checking out v2.5.15.0, configuring with CMake, building the install target, and inspecting dist/lib. Compare the generated symlinks and installed library files with the checked-out version; done means the install output no longer unexpectedly references or retains the previous version.

Written by the indexing model from the issue text.