Fix for release/5.5

5.5 doesn't have any `get*Type()` interfaces, so have to get the types
through some other means.

Author: etcwilde

lib/SIL/IR/TypeLowering.cpp

@@ -2572,7 +2572,8 @@ static CanAnyFunctionType getAsyncEntryPoint(ASTContext &C) {
   // This generates the type signature for @async_main
   // TODO: 'Never' return type would be more accurate.
 
-  CanType returnType = C.getVoidType()->getCanonicalType();
+  CanType returnType =
+      C.getVoidDecl()->getDeclaredInterfaceType()->getCanonicalType();
   FunctionType::ExtInfo extInfo =
       FunctionType::ExtInfoBuilder().withAsync(true).withThrows(false).build();
   return CanAnyFunctionType::get(/*genericSig*/ nullptr, {}, returnType,

lib/SILGen/SILGenFunction.cpp

@@ -938,9 +938,9 @@ void SILGenFunction::emitAsyncMainThreadStart(SILDeclRef entryPoint) {
   // Emit the CreateAsyncTask builtin
   TaskCreateFlags taskCreationFlagMask(0);
   taskCreationFlagMask.setInheritContext(true);
-  SILValue taskFlags =
-      emitWrapIntegerLiteral(moduleLoc, getLoweredType(ctx.getIntType()),
-                             taskCreationFlagMask.getOpaqueValue());
+  SILValue taskFlags = emitWrapIntegerLiteral(
+      moduleLoc, getLoweredType(ctx.getIntDecl()->getDeclaredInterfaceType()),
+      taskCreationFlagMask.getOpaqueValue());
 
   SILValue task =
       emitBuiltinCreateAsyncTask(*this, moduleLoc, subs,