Add GNU Make --shuffle option

GNU Make 4.4 introduced the --shuffle option to randomize the order of
goal targets and prerequisites. This helps detect hidden dependencies
and improve build robustness by exposing order-related issues during
parallel builds.

See:

    https://trofi.github.io/posts/238-new-make-shuffle-mode.html
    https://www.gnu.org/software/make/manual/html_node/Options-Summary.html#index-_002d_002dshuffle

.gitlab-ci.yml

@@ -1083,6 +1083,7 @@ gcc:ossl3:sid:amd64:
     CFLAGS: "${CFLAGS_COMMON} -O3 -DOPENSSL_NO_DEPRECATED=1 -DOPENSSL_API_COMPAT=30000"
     # See https://gitlab.isc.org/isc-projects/bind9/-/issues/3444
     EXTRA_CONFIGURE: "--without-jemalloc --disable-leak-detection"
+    GNUMAKEFLAGS: "--shuffle=reverse"
     RUN_MAKE_INSTALL: 1
   <<: *debian_sid_amd64_image
   <<: *build_job
@@ -1217,6 +1218,7 @@ gcc:tumbleweed:amd64:
     # Doing that requires a DNSRPS provider library to be present on the
     # test host.
     EXTRA_CONFIGURE: "--enable-dnsrps --enable-dnsrps-dl --with-libidn2 ${WITH_READLINE_READLINE}"
+    GNUMAKEFLAGS: "--shuffle=random"
   <<: *tumbleweed_latest_amd64_image
   <<: *build_job