Add the ability to force platform build

Useful for pull requests where we want to build everything to check.

build/com.mbeddr/languages/build.gradle

@@ -71,8 +71,10 @@ ant.taskdef(name: 'junitreport', classname: 'org.apache.tools.ant.taskdefs.optio
 
 def mbeddrDependencies
 
+def usePrebuiltPlatform = ciBuild && !project.hasProperty('forceBuildPlatform')
+
 //on teamcity we don't build the platform we take it from the nexus. Locally we want to build it
-if (ciBuild) {
+if (usePrebuiltPlatform) {
     mbeddrDependencies = [copy_spawner, resolve_mbeddr_platform]
 } else {
     mbeddrDependencies = [copy_spawner, ':build:com.mbeddr:platform:build_platform']