Fix "mvn clean" in libraries/ project

JS examples were failing on "clean" because no phases were set for compilation
and thus they required kotlin-maven-plugin on every phase which is obviously
not built yet when we're running "clean"

libraries/examples/browser-example/pom.xml

@@ -55,6 +55,7 @@
                 <executions>
                     <execution>
                         <id>js</id>
+                        <phase>compile</phase>
                         <goals>
                             <goal>js</goal>
                         </goals>