JVM_IR: mute tests for compiling against Klib

The tests fail currently because Klibs are generated by the JS backend,
and signatures differ between JVM and JS (on JVM, return types are
included in mangles for simple functions).
This leads to linkage errors.
Once signatures are reworked and harmonized between backends, the tests
will repair themselves.

compiler/testData/codegen/boxKlib/properties.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND: JVM_IR
 // FILE: klib.kt
 package fromKlib
 

compiler/testData/codegen/boxKlib/simple.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND: JVM_IR
 // FILE: klib.kt
 package fromKlib