Remove obsolete kotlin.build.useIR flag

(cherry picked from commit 91e47f1fd7)

kotlin-native/build.gradle

@@ -120,15 +120,6 @@ allprojects {
         }
     }
 
-    if (findProperty("kotlin.build.useIR") == "true") {
-        tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
-            kotlinOptions {
-                useIR = true
-                freeCompilerArgs += ["-Xir-binary-with-stable-abi"]
-            }
-        }
-    }
-
     setupHostAndTarget()
     loadCommandLineProperties()
     loadLocalProperties()

kotlin-native/gradle.properties

@@ -34,6 +34,4 @@ ktorVersion=1.2.1
 shadowVersion=5.1.0
 metadataVersion=0.0.1-dev-10
 
-# Uncomment to compile Kotlin/Native backend modules with JVM IR backend.
-# kotlin.build.useIR=true
-kotlinNativeVersionInResources=true
+kotlinNativeVersionInResources=true