[tests] Add test data for KT-54400

compiler/testData/codegen/box/builderInference/issues/kt54400a.kt

@@ -0,0 +1,26 @@
+// ISSUE: KT-54400
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    build {
+        typeVariableMutableProperty = ""
+    }
+    return "OK"
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = "" as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}