Don't override a globally set build option (for ant, gradle, maven or sbt),

especially when there are no jenv options.

plugins/ant/etc/jenv.d/exec/ant-before.bash

@@ -1,4 +1,10 @@
 if [ "$1" = "ant" ]; then            
-  exportVariable ANT_OPTS $JENV_OPTIONS
-  unset JENV_OPTIONS        
-fi
+  if [ -n "$JENV_OPTIONS" ]; then
+    if [ -z "$ANT_OPTS" ]; then
+      exportVariable ANT_OPTS $JENV_OPTIONS
+      unset JENV_OPTIONS        
+    else
+      echo "ANT_OPTS is set and not overridden by jenv" >&2
+    fi
+  fi
+fi

plugins/gradle/etc/jenv.d/exec/gradle-before.bash

@@ -1,4 +1,10 @@
 if [ "$1" = "gradle" ]; then            
-  exportVariable GRADLE_OPTS $JENV_OPTIONS
-  unset JENV_OPTIONS        
-fi
+  if [ -n "$JENV_OPTIONS" ]; then
+    if [ -z "$GRADLE_OPTS" ]; then
+      exportVariable GRADLE_OPTS $JENV_OPTIONS
+      unset JENV_OPTIONS        
+    else
+      echo "GRADLE_OPTS is set and not overridden by jenv" >&2
+    fi
+  fi
+fi

plugins/maven/etc/jenv.d/exec/maven-before.bash

@@ -1,6 +1,10 @@
 if [ "$1" = "mvn" ]; then            
-  if [ -n "$JENV_OPTIONS" -a -z "$MAVEN_OPTS" ]; then
-    exportVariable MAVEN_OPTS $JENV_OPTIONS
-    unset JENV_OPTIONS        
+  if [ -n "$JENV_OPTIONS" ]; then
+    if [ -z "$MAVEN_OPTS" ]; then
+      exportVariable MAVEN_OPTS $JENV_OPTIONS
+      unset JENV_OPTIONS        
+    else
+      echo "MAVEN_OPTS is set and not overridden by jenv" >&2
+    fi
   fi
 fi

plugins/sbt/etc/jenv.d/exec/sbt-before.bash

@@ -1,6 +1,10 @@
 if [ "$1" = "sbt" ]; then            
-  if [ -n "$JENV_OPTIONS" -a -z "$SBT_OPTS" ]; then
-    exportVariable SBT_OPTS $JENV_OPTIONS
-    unset JENV_OPTIONS        
+  if [ -n "$JENV_OPTIONS" ]; then
+    if [ -z "$SBT_OPTS" ]; then
+      exportVariable SBT_OPTS $JENV_OPTIONS
+      unset JENV_OPTIONS        
+    else
+      echo "SBT_OPTS is set and not overridden by jenv" >&2
+    fi
   fi      
-fi
+fi