Use Rust 1.34 for Tor Browser 9
https://bugzilla.mozilla.org/show_bug.cgi?id=1536543 set the Rust requirement to 1.34 and we should follow that if there are no strong reasons against that. While adapting our Rust part we should/could consider the following tasks:
- We don't need to build a newer Rust anymore just for the tor nightlies
- Given our work on the mingw-w64/clang toolchain for legacy/trac#28238 (moved), which requites a pretty new toolchain, we could test using the llvm we already build for that one to compile Rust instead of building an own llvm during Rust build
- We need to switch the target for armv7 to
thumbv7neon-linux-androidabi(see: https://bugzilla.mozilla.org/show_bug.cgi?id=1521734 for more details).