Set Erlang cookie explicitly for running Clouseau

The Erlang cookie shared by the CouchDB and Clouseau nodes goes out
of sync somehow mysteriously which makes the corresponding tests
fail immediately.  Until the exact causes are known, work around
this issue by configuring both sides with the same string (via the
`ERLANG_COOKIE` make variable) and do not rely on other implicit
methods of generating and obtaining the cookie from other sources.

Author: pgj

build-aux/Jenkinsfile

@@ -276,8 +276,8 @@ def generateNativeStage(platform) {
                   retry (3) {sh '$MAKE eunit'}
                   if (meta[platform].quickjs_test262) {retry(3) {sh 'make quickjs-test262'}}
                   retry (3) {sh '$MAKE elixir'}
-                  retry (3) {sh '$MAKE elixir-search'}
-                  retry (3) {sh '$MAKE mango-test'}
+                  retry (3) {sh '$MAKE elixir-search ERLANG_COOKIE=crumbles'}
+                  retry (3) {sh '$MAKE mango-test ERLANG_COOKIE=crumbles'}
                   retry (3) {sh '$MAKE weatherreport-test'}
                   retry (3) {sh '$MAKE nouveau-test'}
                 }
@@ -412,8 +412,8 @@ def generateContainerStage(platform) {
                     retry(3) {sh 'make eunit'}
                     if (meta[platform].quickjs_test262) {retry(3) {sh 'make quickjs-test262'}}
                     retry(3) {sh 'make elixir'}
-                    retry(3) {sh "${setClouseauJavaHome}make elixir-search"}
-                    retry(3) {sh "${setClouseauJavaHome}make mango-test"}
+                    retry(3) {sh "${setClouseauJavaHome}make elixir-search ERLANG_COOKIE=crumbles"}
+                    retry(3) {sh "${setClouseauJavaHome}make mango-test ERLANG_COOKIE=crumbles"}
                     retry(3) {sh 'make weatherreport-test'}
                     retry(3) {sh 'make nouveau-test'}
                   }