Move `systemProp` function to the common module; only the JVM platform implements it properly while others always use provided default value.
diff --git a/kotlinx-coroutines-core/native/src/internal/SystemProps.kt b/kotlinx-coroutines-core/native/src/internal/SystemProps.kt
new file mode 100644
index 0000000..6779d4e
--- /dev/null
+++ b/kotlinx-coroutines-core/native/src/internal/SystemProps.kt
@@ -0,0 +1,7 @@
+/*
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.coroutines.internal
+
+internal actual fun systemProp(propertyName: String): String? = null
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