Previously we maintained three types of builds: a fully internal BUCK build, a
CMake build with modifications to use things from an internal toolchain, and an
open source CMake build.
As far as I'm concerned the intermediate build is not useful because our source
is readily available in both an internal and external form. Use cases as
follows:
1. BUCK build for distributing widely.
2. BUCK build for getting a static binary that can be run on any machine.
3. CMake build for primary development.
4. CMake build for external CI.
With the internal update to CentOS Stream 9 an unmodified CMake build now works
readily. This change patches up some things that were relying on system headers
that should have been vendored and cleans up drgn dependencies.
Test plan:
- It builds.
- TODO: Document CentOS 9 installation.
