Configure the build (`--hl2sdk-root` specifies the path where the all SDKs have been installed by `support/checkout-deps.sh` and `--mms_path` is the path to Metamod: Source).
If you only want to compile using a specific SDK you can hack around the requirement to build for all SDKs by modifying the calls to the SDK constructor in the assignment to `PossibleSDKs` in `AMBuildScript` and setting the `platforms` parameter to \[\] for all SDKs that you don't want to compile for.
### Windows
Use Command Prompt as Gitbash doesn't handle the path arguments correctly.