New build job: compile with ecj

ci.hocon

@@ -221,7 +221,23 @@ gateStyle : ${common} {
     ECLIPSE_EXE : "$ECLIPSE/eclipse"
   }
   run : [
-    ${gateCmd} ["Versions,JDKReleaseInfo,Pylint,Canonicalization Check,BuildJavaWithEcj,BuildJavaWithJavac,IDEConfigCheck,CodeFormatCheck,Checkstyle,Copyright check,UnitTests: ExpectedTestOutput file check,BuildJavaWithEcj"]
+    ${gateCmd} ["Versions,JDKReleaseInfo,Pylint,Canonicalization Check,BuildJavaWithJavac,IDEConfigCheck,CodeFormatCheck,Checkstyle,Copyright check,UnitTests: ExpectedTestOutput file check"]
+  ]
+}
+
+gateBuildWithEcj : ${common} {
+  # need pyhocon fix
+  downloads : {
+    JAVA_HOME : ${java8Downloads.downloads.JAVA_HOME}
+    EXTRA_JAVA_HOMES : ${java8Downloads.downloads.EXTRA_JAVA_HOMES}
+    JDT : {name: ecj, version: "4.5.1", platformspecific: false}
+    ECLIPSE : {name: eclipse, version: "4.5.2", platformspecific: true}
+  }
+  environment : {
+    ECLIPSE_EXE : "$ECLIPSE/eclipse"
+  }
+  run : [
+    ["mx", "build"]
   ]
 }
 
@@ -257,6 +273,7 @@ builds = [
   ${gateTestNoSpecialsLinux}  {capabilities : [linux, amd64, fast],  targets : [gate], name: "gate-test-linux-amd64-nospecials"}
   ${gateTestDarwin}           {capabilities : [darwin_sierra, amd64], targets : [gate], name: "gate-test-darwin-amd64"}
   ${gateStyle}                {capabilities : [linux, amd64],  targets : [gate], name: "gate-style-linux-amd64"}
+  ${gateBuildWithEcj}         {capabilities : [linux, amd64],  targets : [gate], name: "gate-ecj-linux-amd64"}
   ${rbcheck}                  {capabilities : [linux, amd64],  targets : [gate], name: "gate-rbcheck-linux-amd64"}
   ${internalPkgtest}          {capabilities : [linux, amd64],  targets : [gate], name: "gate-internal-pkgtest-linux-amd64"}
   ${gateTestJava9Linux}       {capabilities : [linux, amd64, fast],  targets : [gate], name: "gate-test-java9-linux-amd64"}