nix: Clean up build (#27881)

- bump our livekit version to include a fix for a crane bug (TODO: add
link when an issue is filed on crane)
- switch to a clang stdenv for both linux and macos
- manually unify versions of our notify crate
- remove old linker flags which were only needed for livekit
- fix an issue where RUSTFLAGS shadowed the rustflags from cargo configs

Release Notes:

- N/A

.github/workflows/release_nightly.yml

@@ -184,9 +184,6 @@ jobs:
           - os: arm Mac
             runner: [macOS, ARM64, test]
             install_nix: false
-          - os: arm Linux
-            runner: buildjet-16vcpu-ubuntu-2204-arm
-            install_nix: true
     if: github.repository_owner == 'zed-industries'
     runs-on: ${{ matrix.system.runner }}
     needs: tests