Test with -Zmiri-provenance-gc=1 on Linux

Author: saethlin

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

@@ -25,6 +25,12 @@ cat /tmp/toolstate/toolstates.json
 python3 "$X_PY" test --stage 2 check-tools
 python3 "$X_PY" test --stage 2 src/tools/clippy
 python3 "$X_PY" test --stage 2 src/tools/rustfmt
+
+if [[ "$HOST_TARGET" == "x86_64-unknown-linux-gnu" ]]; then
+    # Set the GC interval to 1 on Linux (run the GC every basic block).
+    # This makes it much more likely we will see GC bugs (the default is every 10000 blocks).
+    export MIRIFLAGS=-Zmiri-provenance-gc=1
+fi
 python3 "$X_PY" test --stage 2 src/tools/miri
 # We natively run this script on x86_64-unknown-linux-gnu and x86_64-pc-windows-msvc.
 # Also cover some other targets via cross-testing, in particular all tier 1 targets.