[Build] Setup useFirForLibraries flag

libraries/stdlib/jdk7/build.gradle

@@ -90,6 +90,8 @@ compileTestKotlin {
     ]
 }
 
+configureFrontendIr(project)
+
 LibrariesCommon.configureJava9Compilation(project, 'kotlin.stdlib.jdk7')
 
 task testJdk6Tests(type: Test) {

libraries/stdlib/jdk8/build.gradle

@@ -75,6 +75,8 @@ compileTestKotlin {
     ]
 }
 
+configureFrontendIr(project)
+
 LibrariesCommon.configureJava9Compilation(project, 'kotlin.stdlib.jdk8')
 
 task testJdk6Tests(type: Test) { thisTask ->

libraries/stdlib/jvm/build.gradle

@@ -143,6 +143,8 @@ compileLongRunningTestKotlin {
     kotlinOptions.freeCompilerArgs += "-opt-in=kotlin.ExperimentalStdlibApi"
 }
 
+configureFrontendIr(project)
+
 task longRunningTest(type: Test, dependsOn: longRunningTestClasses) {
     group = "verification"
     testClassesDirs = sourceSets.longRunningTest.output.classesDirs