TargetDefinition: compare target locations along serialized value

Implementations of ITargetLocation may have an equals() implementation
that does not compare all their serialized attributes. In particular,
this is true for MavenTargetLocation, causing any check for redundancy
upon the 'Apply' button in the Target Platform Preferences Editor to
fail, causing each time:
- the .target file to be rewritten
- the Target Platform State to be re-evaluated

Instead, we compare along the serialized value of ITargetLocation, if
available, ignoring any particular order of target locations as well.

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/target/TargetDefinition.java

@@ -32,6 +32,7 @@
 import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.ParserConfigurationException;
@@ -879,7 +880,7 @@ public boolean isContentEqual(ITargetDefinition definition) {
 				Objects.equals(getVMArguments(), definition.getVMArguments()) && //
 				Objects.equals(getJREContainer(), definition.getJREContainer()) && //
 				Arrays.equals(getIncluded(), definition.getIncluded()) && //
-				Arrays.equals(getTargetLocations(), definition.getTargetLocations()) && //
+				unorderedArraysEqualsSerialized(getTargetLocations(), definition.getTargetLocations()) && //
 				Arrays.equals(getImplicitDependencies(), definition.getImplicitDependencies());
 	}
 
@@ -899,10 +900,24 @@ public boolean isContentEquivalent(ITargetDefinition definition) {
 				isArgsNullOrEqual(getVMArguments(), definition.getVMArguments()) && //
 				Objects.equals(getJREContainer(), definition.getJREContainer()) && //
 				Arrays.equals(getIncluded(), definition.getIncluded()) && //
-				Arrays.equals(getTargetLocations(), definition.getTargetLocations()) && //
+				unorderedArraysEqualsSerialized(getTargetLocations(), definition.getTargetLocations()) && //
 				Arrays.equals(getImplicitDependencies(), definition.getImplicitDependencies());
 	}
 
+	private static boolean unorderedArraysEqualsSerialized(ITargetLocation[] one, ITargetLocation[] two) {
+		if (one == two) {
+			return true;
+		}
+		if (one == null || two == null || one.length != two.length) {
+			return false;
+		}
+		Set<Object> oneXml = Arrays.stream(one).filter(Objects::nonNull)
+				.map(l -> Objects.requireNonNullElse(l.serialize(), l)).collect(Collectors.toSet());
+		Set<Object> twoXml = Arrays.stream(two).filter(Objects::nonNull)
+				.map(l -> Objects.requireNonNullElse(l.serialize(), l)).collect(Collectors.toSet());
+		return oneXml.equals(twoXml);
+	}
+
 	private boolean isArgsNullOrEqual(String args1, String args2) {
 		return (args1 == null && args2 == null)
 				|| Arrays.equals(DebugPlugin.parseArguments(args1), DebugPlugin.parseArguments(args2));