Added Jenkinsfile for automatic build verification (#189)

Script file for automatically building every change in Jenkins (Job set up in https://jenkins-internal.mbed.com/job/mbed-os-morpheus/)

Jenkinsfile

@@ -0,0 +1,61 @@
+// List of targets to compile
+def morpheusTargets = [
+  //"LPC1768",
+  //"NUCLEO_F401RE",
+  //"NRF51822",
+  "K64F"
+  ]
+  
+// Map morpheus toolchains to compiler labels on Jenkins
+def toolchains = [
+  //ARM: "armcc",
+  GCC_ARM: "arm-none-eabi-gcc"
+  ]
+  
+// Initial maps for parallel build steps
+def stepsForParallel = [:]
+ 		 
+// Jenkins pipeline does not support map.each, we need to use oldschool for loop
+for (int i = 0; i < morpheusTargets.size(); i++) {
+  for(int j = 0; j < toolchains.size(); j++) {
+    def target = morpheusTargets.get(i)
+    def toolchain = toolchains.keySet().asList().get(j)
+    def compilerLabel = toolchains.get(toolchain)  
+    
+    def stepName = "${target} ${toolchain}"
+    stepsForParallel[stepName] = morpheusBuildStep(target, compilerLabel, toolchain)
+  }
+}
+
+/* Jenkins does not allow stages inside parallel execution, 
+ * https://issues.jenkins-ci.org/browse/JENKINS-26107 will solve this by adding labeled blocks
+ */
+stage "parallel build"
+try {
+  // Actually run the steps in parallel - parallel takes a map as an argument, hence the above.
+  parallel stepsForParallel
+  
+} catch (err) {
+  currentBuild.result = 'FAILURE'
+  mail to: 'iot-eng-mgmt@arm.com', 
+  subject: "${env.JOB_NAME} build failed",
+  body: "Greetings from mbed Continous integration system. This is an automatic email sent because a build has failed.\n\n\
+This CI job checks the compiling of mbed-os with morpheus from Master branch.\n\n\
+mbed-os build from branch ${env.BRANCH_NAME} has failed.\nSee ${env.BUILD_URL} for details\n\n\
+Regards,\n\
+ARM mbed Continuos Integration"
+} 
+
+//Create yotta build steps for parallel execution
+ def morpheusBuildStep(target, compilerLabel, toolchain) {
+    return {
+      node ("${compilerLabel}") {
+        deleteDir()
+        dir("mbed-os") {
+          checkout scm
+          sh "mbed deploy --protocol ssh"
+          sh "mbed compile -m ${target} -t ${toolchain} -c"
+        }
+      }
+    }
+ }