build/bot: try installing gcc-multilib in linux container

build/bot/Dockerfile.linux

@@ -1,5 +1,9 @@
 FROM golang:1.19.1
 
+# Install build tools.
+RUN apt-get update
+RUN apt-get -yq --no-install-suggests --no-install-recommends install gcc-multilib g++-multilib
+
 # The repo checkout is mounted to /source.
 WORKDIR /source
 
@@ -9,4 +13,4 @@ RUN git config --global --add safe.directory /source
 # Configure Go tool cache locations
 ENV GOPATH=/cache/go
 ENV GOCACHE=/cache/go/cache
-ENV GOMODCACHE=/cache/go/modcache
+ENV GOMODCACHE=/cache/go/modcache