Fix output getting deleted during 2nd pass of incremental compilation

Author: oliviernotteghem

src/main/kotlin/io/bazel/kotlin/builder/tasks/KotlinBuilder.kt

@@ -294,8 +294,17 @@ internal constructor(
           argMap.optional(KotlinBuilderFlags.COMPILER_PLUGIN_CLASS_PATH) ?: emptyList(),
         )
 
+        // Kotlin compiler always requires absolute path for source input in incremental mode
+        val useAbsolutePath = argMap.optionalSingle(KotlinBuilderFlags.INCREMENTAL_COMPILATION) == "true"
         argMap
           .optional(KotlinBuilderFlags.SOURCES)
+          ?.map {
+            if (useAbsolutePath) {
+              FileSystems.getDefault().getPath(it).toAbsolutePath().toString()
+            } else {
+              it
+            }
+          }
           ?.iterator()
           ?.partitionJvmSources(
             { addKotlinSources(it) },