Parametrized build with branch-spec.

-Dbranch-spec=master or release/1.26.0, etc. can
now be used to run the build based on different
versions of the Simantics SDK.

refs #6879

org.simantics.fmil.parent/pom.xml

@@ -6,16 +6,20 @@
 	<version>0.0.1-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
+        <!-- common settings for all modules -->
         <properties>
+                <branch-spec>master</branch-spec>
+                <simantics-download-site>http://www.simantics.org/download</simantics-download-site>
                 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
                 <tycho-version>0.26.0</tycho-version>
         </properties>
 
         <repositories>
+                <!-- configure p2 repository to resolve against -->
                 <repository>
                         <id>simantics-sdk</id>
                         <layout>p2</layout>
-			<url>http://www.simantics.org/download/master/sdk</url>
+                        <url>${simantics-download-site}/${branch-spec}/sdk</url>
                 </repository>
         </repositories>