[Maven] Kotlin compiler plugin should respect model's compile source roots

#KT-13995 Fixed

Merge-request: KT-MR-8236
Merged-by: Aleksei Cherepanov <aleksei.cherepanov@jetbrains.com>

libraries/tools/kotlin-maven-plugin/src/main/java/org/jetbrains/kotlin/maven/KotlinCompileMojoBase.java

@@ -74,8 +74,10 @@ public abstract class KotlinCompileMojoBase<A extends CommonCompilerArguments> e
     private boolean multiPlatform = false;
 
     protected List<String> getSourceFilePaths() {
-        if (sourceDirs != null && !sourceDirs.isEmpty()) return sourceDirs;
-        return project.getCompileSourceRoots();
+        List<String> list = new ArrayList<>();
+        if (sourceDirs != null && !sourceDirs.isEmpty()) list.addAll(sourceDirs);
+        list.addAll(project.getCompileSourceRoots());
+        return list;
     }
 
     @NotNull