Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
Sources/main.c:1:10: fatal error: stm32f446xx.h: No such file or directory
    1 | #include "stm32f446xx.h"
      |          ^~~~~~~~~~~~~~~
compilation terminated.
Target //:firmware failed to build
INFO: Elapsed time: 0.180s, Critical Path: 0.04s

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
Sources/main.c:1:10: fatal error: stm32f446xx.h: No such file or directory
    1 | #include "stm32f446xx.h"
      |          ^~~~~~~~~~~~~~~
compilation terminated.
Target //:firmware failed to build
INFO: Elapsed time: 0.180s, Critical Path: 0.04s