Bad file install locations

### Problem

The 1.13.6.1 release installs some new files that are not in acceptable locations.

All `.cmake` files should be installed into one location. Extra support scripts should be installed under `share` not at the top of the filesystem.

**Expected behavior:**

A clean install with files in expected locations

**Actual behavior:**

cmake config files and extra support scripts are installed into two locations.

### Versions

* OSL branch/version: 1.13.6.1

### Solution

`llvm_macros.cmake` should have `DESTINATION ${OSL_CONFIG_INSTALL_DIR}` to put it with the other cmake files.

The `serialize-bc.py` script would be better installed somewhere like `DESTINATION ${CMAKE_INSTALL_DATADIR}/build-scripts`

Search the install rules for llvm_macros.cmake and serialize-bc.py, then inspect the surrounding CMake installation definitions. Make a clean install of version 1.13.6.1 and verify that all .cmake files share the configured location while serialize-bc.py is under the CMake data directory's build-scripts path.

Written by the indexing model from the issue text.