Properly export LIBCLANG_PATH

[svenstaro]

Fixes #5.

[jessebraham]

Sorry I'm not entirely sure I understand what's going on here (I also have not seen this error personally). Shouldn't LIBCLANG_PATH already be set by the export script? See here:

Building the export script:
https://github.com/esp-rs/rust-build/blob/main/install-rust-toolchain.sh#L504

Updating the path:
https://github.com/esp-rs/xtensa-toolchain/blob/main/install.sh#L58-L59

[brianmay]

I think I understand. The problem is that github CI doesn't support the export script. While we do run the export script, the changes will get lost as soon as the install.sh script finishes.

We have to use the supported github mechanism for updating environment variables for future CI steps. We were doing this for $PATH but we were not doing this for $LIBCLANG_PATH which I presume is a new required value that was introduced recently.

Confirmed this change fixes the problem for me.

I note that we do not preserve the $PIP_USER environment variable either. Which is set to "NO". But so far it doesn't look like this actually causes any problems.

[HannesGitH]

for peeps coming here because they tried cargo generate --git https://github.com/esp-rs/esp-idf-template cargo and then directly cargo run, you are still using the upstream rust which has no xtensa target, you need to use the rust fork (via . ./export-esp.sh) as specified here