Also, use the finalAttrs pattern for easier overrides.
Explicitly mention that we don't fetch submodules to emphasize that
all vendored dependencies are replaced with nix dependencies.
Update UHDM and also fix for Darwin build.
The gtest version used in the project unconditionally uses
/tmp as temporary directory in Darwin and does not honor the
environment variables introduced in gtest 1.12.
Use that gtest version so that it will work in the Hydra
build environment.
Related: #199919 as this is fixing the Darwin build.
Signed-off-by: Henner Zeller <h.zeller@acm.org>
