BDE tools does not install files under the BdeBuildSystem directory that are necessary at run-time

Perhaps mistakenly, I operated under the assumption that BDE tools may be installed by running `cmake --install`. However, this installation does not contain any files under the `BdeBuildSystem` directory that seem required at run-time.

**To Reproduce:**
1. Run `cmake -B -S --install-prefix
2. Run `cmake --install
3. Notice a bunch of the `bbs_build` is installed to `` but not any files in the `BdeBuildSystem` directory
4. Set to the PATH
5. Run `bbs_build configure`
6. Error: Cannot find BdeBuildSystem cmake modules

I expect to be able to use the result of installing this repository. This error does not occur when I run `bbs_build` from the directory into which I clone the repository.

**Environment:**
- Darwin G7WH7WFVKV 21.6.0 Darwin Kernel Version 21.6.0

Start by reproducing the documented `cmake --install` steps and tracing how `bbs_build configure` locates the `BdeBuildSystem` CMake modules. Compare the installed tree under the prefix with the repository tree, focusing on the `BdeBuildSystem` directory and `bbs_build` entry point. Done means an installed copy can run `bbs_build configure` without the missing-module error.

Written by the indexing model from the issue text.