Despite this name not being in the runfiles manifest, this works in
Bazel because of how the module and workspace are configured. I should
have realized that as it was used elsewhere as well. This should
consolidate all of our runfiles paths to use the exact same patterns
now. These were the only remaining divergences.
This removes the `data_dir` from the driver favoring the installation
abstraction for the both locating the prelude and linking utilities.
With this, an installed toolchain should also be able to compile and
link Carbon successfully, and the build of the examples should exercise
this path almost exactly. (The only difference is using the driver
`cc_binary` directly rather than relying on the symlink from inside the
install tree.)
The install directory contains the BUILD logic for creating an
installable tree of data files and executables for the toolchain, and
a library to facilitate toolchain code accessing the paths to their data
within this installation.
Then adds an installation of LLD in a synthetic LLVM installation, and
teaches the Clang runner to configure this and use it for linking
instead of the system linker.
Currently, the install paths only really manage access to the LLVM
binaries installed and used by the Clang runner for linking, but
eventually other data files like the prelude and runtime libraries will
be fleshed out as well. There are TODOs for moving more things over here
such as the prelude.
One interesting aspect of this is where to put helpers like parts of
LLVM in our install. This PR suggests nesting those files under
`lib/carbon`. While using a `lib` subdirectory isn't a perfect fit for
the FHS (Filesystem Hierarchy Standard), having a single location where
private data is collected is significantly superior to spreading them
across the system. This also matches similar patterns used by Clang
itself and several other language toolchains and standard libraries.
The install directory also provides a natural place for us to build out
packaging rules to create installable packages in various formats, but
that remains future work.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Chandler Carruth
Jon Ross-Perkins