Build: add kotlin.build.useIRForLibraries to enable JVM IR for libraries separately

The next step for JVM IR adoption in our project is going to be enabling
`kotlin.build.useIR`, but keeping `kotlin.build.useIRForLibraries`
disabled until we fix all remaining ABI incompatibility issues for
library code.

libraries/reflect/api/build.gradle

@@ -52,6 +52,8 @@ compileKotlin {
     }
 }
 
+configureJvmIrBackend(project)
+
 jar {
     manifestAttributes(manifest, project, "internal")
 }