Make Throwable.addSuppressed extension work without kotlin-stdlib-jdk7*

*given that it runs on JDK7 and higher. The addSuppressed member
is called with reflection when it's available.
kotlin-stdlib-jdk7 extension still overrides that and calls
addSuppressed member statically as before.

#KT-30560 Fixed

libraries/stdlib/jvm/src/kotlin/internal/PlatformImplementations.kt

@@ -5,14 +5,24 @@
 
 package kotlin.internal
 
+import java.lang.reflect.Method
 import java.util.regex.MatchResult
 import kotlin.random.FallbackThreadLocalRandom
 import kotlin.random.Random
 
 internal open class PlatformImplementations {
 
+    private object ReflectAddSuppressedMethod {
+        @JvmField
+        public val method: Method? = Throwable::class.java.let { throwableClass ->
+            throwableClass.methods.find {
+                it.name == "addSuppressed" && it.parameterTypes.singleOrNull() == throwableClass
+            }
+        }
+    }
+
     public open fun addSuppressed(cause: Throwable, exception: Throwable) {
-        // do nothing
+        ReflectAddSuppressedMethod.method?.invoke(cause, exception)
     }
 
     public open fun getMatchResultNamedGroup(matchResult: MatchResult, name: String): MatchGroup? {

libraries/stdlib/jvm/test/ExceptionJVMTest.kt

@@ -65,4 +65,11 @@ class ExceptionJVMTest {
         exception.stackTrace = stackTrace
         assertArrayNotSameButEquals(stackTrace, exception.stackTrace)
     }
+
+    @Test fun addSuppressedDoesNotThrow() {
+        val e1 = Throwable()
+        val e2 = Exception("Suppressed")
+
+        e1.addSuppressed(e2)
+    }
 }