Prevent JS optimizer from inserting duplicate variable declarations

js/js.translator/testData/inlineSizeReduction/cases/noDuplicateVariableDeclaration.kt

@@ -0,0 +1,28 @@
+package foo
+
+// CHECK_VARS_COUNT: function=test_za3lpa$ count=2
+
+inline fun if1(f: (Int) -> Int, a: Int, b: Int, c: Int): Int {
+    val result = f(a)
+
+    if (result == b) {
+        return f(a)
+    }
+
+    return f(c)
+}
+
+fun test(x: Int): Int {
+    val test1 = if1({ it }, x, 2, 3)
+    return test1
+}
+
+fun box(): String {
+    var result = test(2)
+    if (result != 2) return "fail1: $result"
+
+    result = test(100)
+    if (result != 3) return "fail2: $result"
+
+    return "OK"
+}