works?

circleci/images/exttester/Dockerfile

@@ -1,6 +1,14 @@
+FROM buildpack-deps:bullseye AS bullseye-no-libpq
+
+RUN <<'EOF'
+    rm /usr/lib/x86_64-linux-gnu/libpq.so*
+
+    DEBIAN_FRONTEND=noninteractive apt purge -y libpq5
+EOF
+
 # postgres doesn't ship their isolation tester in the server-dev images
 # we use this builder to build the isolation tester from a specific version
-FROM buildpack-deps:bullseye AS dev-tools-builder
+FROM bullseye-no-libpq AS dev-tools-builder
 
 RUN <<'EOF'
 # install dependencies
@@ -65,7 +73,7 @@ WORKDIR /build/postgresql-${PG_VERSION_CLEAN}/build
 RUN ../configure --prefix /usr/lib/postgresql/${PG_MAJOR}/
 RUN make -sj8
 
-FROM buildpack-deps:bullseye AS dev-tools-collection
+FROM bullseye-no-libpq AS dev-tools-collection
 
 WORKDIR /collect
 
@@ -84,7 +92,7 @@ COPY --from=dev-tools-builder /build/postgresql-${PG_VERSION_CLEAN}/build/src/te
 COPY --from=dev-tools-builder /build/postgresql-${PG_VERSION_CLEAN}/src/test/regress/ usr/lib/postgresql/${PG_MAJOR}/lib/regress/
 RUN rm -rf usr/lib/postgresql/${PG_MAJOR}/lib/regress/*.c usr/lib/postgresql/${PG_MAJOR}/lib/regress/*.h
 
-FROM buildpack-deps:bullseye
+FROM bullseye-no-libpq
 
 # add unpriviliged user for tests
 RUN useradd -ms /bin/bash circleci
@@ -170,15 +178,6 @@ apt-get install -y --no-install-recommends --allow-downgrades \
     postgresql-${PG_MAJOR}-dbgsym=${pgdg_version} \
     postgresql-server-dev-${PG_MAJOR}=${pgdg_version} \
     postgresql-${PG_MAJOR}-wal2json \
-
-
-DEBIAN_FRONTEND=noninteractive apt purge -y \
-    libpq5 \
-
-# remove libpq.so and the symlinkes to it, if any
-[ -n "$(ls /usr/lib/x86_64-linux-gnu/libpq.so* 2>/dev/null)" ] && rm /usr/lib/x86_64-linux-gnu/libpq.so*
-
-apt-get install -y --no-install-recommends --allow-downgrades \
     libpq-dev=${pgdg_version} \
     libpq5=${pgdg_version} \