Rollup merge of #77991 - Aaron1011:bump-backtrace-again, r=Mark-Simulacrum

JohnTitor · web-flow · commit b4282b37f167 · 2020-10-17T05:36:50.000+09:00
Bump backtrace-rs This pulls in rust-lang/backtrace-rs#376, which fixes Miri support for `std::backtrace::Backtrace`.
diff --git a/library/backtrace b/library/backtrace
@@ -1 +1 @@
-Subproject commit 893fbb23688e98376e54c26b59432a2966a8cc96
+Subproject commit a6dd47bd588c882e735675a1379d2b61719fa380
