bug: illegal rust lib.rs breaks `kit build --hyperapp` without good error message

[nick1udwig]

ERROR src/main.rs:1352: 
   0: Error processing project /home/nick/git/voice/voice: Failed to parse lib.rs for project: /home/nick/git/voice/voice

Location:
   src/build/wit_generator.rs:1312

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ SPANTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

   0: kit::build::wit_generator::generate_wit_files
      at src/build/wit_generator.rs:1267
   1: kit::build::execute
      at src/build/mod.rs:1704
   2: kit::execute
      at src/main.rs:134

we should probably just pass this through to cargo build so we can get out their nice errors

[jurij-jukic]

Merged here. #379