Checkout a commit beyond 2022g. 2022g itself does not compile, but a downstream
commit allows us to compile and achieve parity with 17.0.0's time zone data.
tz's makefile can only build in-tree. It *installs* to a different
directory (specified by `DESTDIR`), but the build artifacts are left in
the source tree, including `zic.o`, `zic`, etc. This is disruptive to
CMake builds which are usually out-of-tree. To work around this, copy
the whole source tree to a path under `CMAKE_CURRENT_BINARY_DIR`, and
build it from there. It's a tiny project so the cost of copying is not
significant.
