Updating abseil

The BUILD.bazel file for the abseil build is parsed via the generated ninja file from the native abseil cmake build. The parse_libs_from_ninja.py will perform the parsing and generation of the BUILD.bazel file.

To update abseil you should:

1. update the version/repo information in the import.py script
2. remove the existing abseil-cpp/dist directory
3. run the import.sh script

Mongodbtoolchain dependency

Note that the parse_libs_from_ninja.py assumes the mongodb toolchain is installed and access cmake via the toolchain. If this is not the case you will need to update the script for you particuler environment.