[tbb-bugs] #26329 [Applications/Tor Browser]: Rust invocation for Firefox on 32bit Windows is failing

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#26329: Rust invocation for Firefox on 32bit Windows is failing
-------------------------------------+-------------------------------------
     Reporter:  gk                   |      Owner:  tbb-team
         Type:  defect               |     Status:  new
     Priority:  Very High            |  Milestone:
    Component:  Applications/Tor     |    Version:
  Browser                            |   Keywords:  ff60-esr,
     Severity:  Normal               |  TorBrowserTeam201806
Actual Points:                       |  Parent ID:  #26203
       Points:                       |   Reviewer:
      Sponsor:                       |
-------------------------------------+-------------------------------------
 Firefox's configure is failing when checking for a functional `rustc` with
 {{{
  0:32.86 DEBUG: Executing: `/var/tmp/dist/rust/bin/rustc --crate-type
 staticlib --target=i686-pc-windows-gnu -o /tmp/conftest66YTEr.rlib
 /tmp/conftestkSgS7j.rs`
  0:32.86 DEBUG: The command returned non-zero exit status 101.
  0:32.86 DEBUG: Its error output was:
  0:32.86 DEBUG: | error: the crate `panic_unwind` does not have the panic
 strategy `unwind`
  0:32.86 DEBUG: |
  0:32.86 DEBUG: | error: aborting due to previous error
  0:32.86 DEBUG: |
  0:32.86 ERROR: Cannot compile for i686-w64-mingw32 with
 /var/tmp/dist/rust/bin/rustc
 }}}

 Firefox is getting compiled with `panic=abort` (https://dxr.mozilla.org
 /mozilla-central/source/testing/geckodriver/.cargo/config) for 32bit
 Windows and we intend to create a Rustc compiler with that panic strategy
 as well, given that cross-compiling with `panic=unwind` is not working
 (see: comment:1:ticket:25894).

 While compiling every crate in the std lib with `panic-abort` is working
 it seems we still miss some crucial bit here.

 One option to test would be if we can get rid of `panic_unwind` if we
 don't need it anyway when compiling for 32bit Windows. For what it is
 worth, the compiler as we have it right now is working for `tor` compiled
 with Rust.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26329>
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