CI: disable rustc debug assertions for mingw-check

AFAIK `mingw-check` is intended for fast-rejection, so disable
`rust.debug-assertions` (as it would be lying to say CI rustc has debug
assertions).

Author: jieyouxu

src/ci/docker/host-x86_64/mingw-check/Dockerfile

@@ -43,6 +43,9 @@ COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/
 
 ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
 
+# NOTE(jieyouxu): CI rustc do not have rustc debug assertions at the moment!
+ENV NO_DEBUG_ASSERTIONS 1
+
 # Check library crates on all tier 1 targets.
 # We disable optimized compiler built-ins because that requires a C toolchain for the target.
 # We also skip the x86_64-unknown-linux-gnu target as it is well-tested by other jobs.