syntax: Suppress panic message on `fatal`

This commit ensures that the rustc thread does not leak a panic message whenever
a call to `fatal` happens. This already happens for the main rustc thread as
part of the `rustc_driver::monitor` function, but the compiler also spawns
threads for other operations like `-C codegen-units`, and sometimes errors are
emitted on these threads as well. To ensure that there's a consistent
error-handling experience across threads this unifies these two to never print
the panic message in the case of a normal and expected fatal error.

This should also fix the flaky `asm-src-loc-codegen-units.rs` test as the output
is sometimes garbled if diagnostics are printed while the panic message is also
being printed.

0 files changed, 0 insertions, 0 deletions