Ensure RUSTFLAGS is passed through on cross compile (#1529)
Ensure RUSTFLAGS is passed through on cross compile (#1529)

## Issue Addressed

NA

## Proposed Changes

Tells `cross` (used for cross-compiling) to read the `RUSTFLAGS`env and pass it through during build. This allows us to use `-g` and get debug info. 

## Additional Info

NA




sigp/lighthouse,sigp/lighthouse,sigp/lighthouse,sigp/lighthouse