Bug 1674773 - make tsan builds use consistent flags. r=rstewart

This makes --enable-thread-sanitizer turn on Rust tsan (-Zsanitizer=thread).
This requires changing SpiderMonkey tsan to use the tsan rust nightly.

In future changes, more Rust tsan integration will key off of MOZ_TSAN.

Differential Revision: https://phabricator.services.mozilla.com/D96453

browser/config/mozconfigs/linux64/tsan

@@ -18,9 +18,6 @@ export MOZ_PKG_SPECIAL=tsan
 # Disable telemetry
 ac_add_options MOZ_TELEMETRY_REPORTING=
 
-# Ensure Rust also gets the necessary instrumentation
-export RUSTFLAGS="-Zsanitizer=thread"
-
 # rustfmt is currently missing in Rust nightly
 unset RUSTFMT
 

config/makefiles/rust.mk

@@ -53,6 +53,11 @@ ifeq (1,$(MOZ_PARALLEL_BUILD))
 cargo_build_flags += -j1
 endif
 
+# This should also be paired with -Zbuild-std, but that doesn't work yet.
+ifdef MOZ_TSAN
+RUSTFLAGS += -Zsanitizer=thread
+endif
+
 # These flags are passed via `cargo rustc` and only apply to the final rustc
 # invocation (i.e., only the top-level crate, not its dependencies).
 cargo_rustc_flags = $(CARGO_RUSTCFLAGS)

taskcluster/ci/spidermonkey/linux.yml

@@ -237,7 +237,7 @@ sm-tsan-linux64/opt:
         toolchain:
             - linux64-binutils
             - linux64-clang
-            - linux64-rust
+            - linux64-rust-nightly
             - linux64-dump-syms
 
 sm-rootanalysis-linux64/debug: