Always run codegen when IC is enabled

We may need to run code generation when no source files are specified
for incremental compilation (to update caches & metadata)

jps-plugin/testData/incremental/pureKotlin/classRemoved/A.kt

@@ -0,0 +1,3 @@
+package test
+
+class A

jps-plugin/testData/incremental/pureKotlin/classRemoved/A.kt.delete.1

@@ -0,0 +1 @@
+

jps-plugin/testData/incremental/pureKotlin/classRemoved/build.log

@@ -0,0 +1,10 @@
+================ Step #1 =================
+
+Cleaning output files:
+  out/production/module/META-INF/module.kotlin_module
+  out/production/module/test/A.class
+End of files
+Compiling files:
+End of files
+Exit code: OK
+------------------------------------------

jps-plugin/testData/incremental/pureKotlin/classRemoved/other.kt

@@ -0,0 +1,4 @@
+package test
+
+fun other() {
+}