rustc_compile_action doesn't pass default_shell_env

[granaghan]

I have a CC toolchain where most of the "tools" are actually shell script wrappers that ensure only toolchain provided libraries are loaded. This involves some calls to readlink and dirname. rust_compile_actions doesn't set use_default_shell_env to True and as a result, these fail when rustc calls clang which in turn calls ld.lld. I found that setting use_default_shell_env = True resolved my issue.` Is this a change that can be made? Or should we consider adding a setting to either the rust toolchain or add another provider that can be applied to CC toolchains so we can let users configure this?

rules_rust/rust/private/rustc.bzl

Line 1258 in aa4b3a8

ctx.actions.run(