When using `clangd` for cross-compiled projects, it's necessary to use the `--query-driver` flag so that `clangd` can extract the compiler's built-in header paths. However, there's no such flag for `clangd-indexer` so we're unable to build a working static index for these projects.
This patch adds a `--query-driver` flag to `clangd-indexer` for this scenario.
I saw some tests under `clang-tools-extra/clangd/test/` but I think the cross-compilation case is a bit more complex to test. Let me know if you'd like me to look into this further.
Resolves: https://github.com/clangd/clangd/issues/1717
Reviewed By: nridge
Differential Revision: https://reviews.llvm.org/D157990
109bc024c8