Large build size of gf180mcu

[kareefardi]

For version bdc9412b3e468c102d01b7cf6337be06ec6e9c9a of gf180mcu if all variants are enabled the total size is about 7.6 GB. Each variant has a size of 1.9 GB. libs.tech/klayout has a size of 1.2 GB for each variant. There are two "issues" here:

1. lvs folder inside libs.tech/klayout is duplicated. It is present once as libs.tech/klayout/lvs and the other as libs.tech/klayout/tech/lvs.
2. lvs and drc folders have testing data inside (although drc folder has much smaller size) which accounts for most of the size of klayout folder. I don't think this data is needed as part of the PDK build.

This is not a breaking issue and if it is decided to resolve this issue, there are the following suggestions:

1. Move the testing data outside of globalfoundries-pdk-libs-gf180mcu_fd_pv repo.
2. While building the PDK, explicitly remove the testing data.
3. The testing data can be an optional output of the build.
4. Finally, symlink common files of the testing data (perhaps other build output).

Note:
This is entirely based on the PDK build of volare. I could open an issue there, but I believe opening it in open_pdks will provide more insight and is a better place for such discussion.