toolchain-utils: Fix paths related to sysroot in rust-analyzer wrapper

Currently when trying to open e.g. a standard library type's source
in VSCode, rust-analyzer-chromiumos-wrapper will point to the wrong
path. That is, because inside chroot, rust's sysroot lives under /usr,
while outside of the chroot it usually lives under $HOME/.rustup.

This patch adds the capability for translating these sysroot related
paths accordingly.

BUG=b:324045239, b:320674356
TEST=manual

Change-Id: Id0a01409a8622159cad136485f7b8c077a19fbc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5272425
Reviewed-by: George Burgess <[email protected]>
Commit-Queue: Bastian Kersting <[email protected]>
Tested-by: Bastian Kersting <[email protected]>
1 file changed