Merge pull request swiftlang#70157 from mikeash/fix-findBridgeWitness-5.10

[5.10][Runtime] Fix findBridgeWitness when building for the shared cache.

Author: mikeash

stdlib/public/runtime/DynamicCast.cpp

@@ -208,9 +208,8 @@ PROTOCOL_DESCR_SYM(s21_ObjectiveCBridgeable);
 
 static const _ObjectiveCBridgeableWitnessTable *
 findBridgeWitness(const Metadata *T) {
-  static const auto bridgeableProtocol
-    = &PROTOCOL_DESCR_SYM(s21_ObjectiveCBridgeable);
-  auto w = swift_conformsToProtocolCommon(T, bridgeableProtocol);
+  auto w = swift_conformsToProtocolCommon(
+      T, &PROTOCOL_DESCR_SYM(s21_ObjectiveCBridgeable));
   return reinterpret_cast<const _ObjectiveCBridgeableWitnessTable *>(w);
 }