[kotlin compiler] use the last version of plugin kotlinVersion with embedded compiler of buildKotlinVersion

the buildKotlinVersion down to 1.3.50-dev-787

gradle.properties

@@ -15,8 +15,8 @@
 #
 
 # A version of the Kotlin "toolchain" (compiler, runtime, stdlib etc) used by the build script.
-buildKotlinVersion=1.3.50-dev-1010
+buildKotlinVersion=1.3.50-dev-787
-buildKotlinCompilerRepo=https://teamcity.jetbrains.com/guestAuth/app/rest/builds/buildType:(id:Kotlin_dev_Compiler),number:1.3.50-dev-1010,branch:default:any,pinned:true/artifacts/content/maven
+buildKotlinCompilerRepo=https://teamcity.jetbrains.com/guestAuth/app/rest/builds/buildType:(id:Kotlin_dev_Compiler),number:1.3.50-dev-787,branch:default:any,pinned:true/artifacts/content/maven
 remoteRoot=konan_tests
 kotlinCompilerRepo=https://teamcity.jetbrains.com/guestAuth/app/rest/builds/buildType:(id:Kotlin_dev_Compiler),number:1.3.50-dev-1050,branch:default:any,pinned:true/artifacts/content/maven
 kotlinVersion=1.3.50-dev-1050

gradle/kotlinGradlePlugin.gradle

@@ -20,5 +20,17 @@ project.buildscript.repositories {
 }
 
 project.buildscript.dependencies {
-    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$buildKotlinVersion"
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
 }
+configurations {
+    kotlinCompilerClasspath
+}
+project.repositories {
+    maven {
+        url kotlinCompilerRepo
+    }
+}
+
+project.dependencies {
+    kotlinCompilerClasspath("org.jetbrains.kotlin:kotlin-compiler-embeddable:$buildKotlinVersion")
+}