LLVM_PROFILER_RT_LIB may be set to an absolute path (e.g., in Fedora builds),
but `-l` expects a library name, not a path. After #138273, this caused builds
to fail with a "could not find native static library" error.
This patch updates the build script to split the path into directory and
filename, using `cargo::rustc-link-search` for the directory and
`cargo::rustc-link-lib=+verbatim` for the file. This allows profiler_builtins to
correctly link the static library even when an absolute path is provided.
This behaviour was introduced during the upgrade to LLVM 11. Now that the list
of source files has been cleaned up, we can reasonably expect _all_ of the
listed source files to be present.
The current `build.rs` will automatically skip source files that don't exist.
An unfortunate side-effect is that if _no_ files could be found (e.g. because
the directory was wrong), the build fails with a mysterious linker error.
We can reduce the awkwardness of this by explicitly checking that at least one
source file was found.
Currently, when building with `build-std`, some library build scripts
check properties of the target by inspecting the target triple at
`env::TARGET`, which is simply set to the filename of the JSON file
when using JSON target files.
This patch alters these build scripts to use `env::CARGO_CFG_*` to
fetch target information instead, allowing JSON target files
describing platforms without `restricted_std` to build correctly when
using `-Z build-std`.
Fixes wg-cargo-std-aware/#60.
This changes the bootstrap config `target.*.profiler` from a plain bool
to also allow a string, which will be used as a path to the pre-built
profiling runtime for that target. Then `profiler_builtins/build.rs`
reads that in a `LLVM_PROFILER_RT_LIB` environment variable.
All other Platform files included in `llvm-project/compiler-rt` were
present, except Fuchsia.
Now that there is a functional end-to-end version of
`-Zinstrument-coverage`, I need to start building and testing
coverage-enabled Rust programs on Fuchsia, and this file is required.
