[Embedded] Treat the entrypoint function as having a unique definition

This ensures that one can use deferred code generation everywhere with
Embedded Swift and still get the appropriate entry symbol emitted.

Author: DougGregor

lib/SIL/IR/SILFunction.cpp

@@ -558,6 +558,10 @@ bool SILFunction::hasNonUniqueDefinition() const {
   if (!getASTContext().LangOpts.hasFeature(Feature::Embedded))
     return false;
 
+  // If this function is the entrypoint, it is unique.
+  if (getName() == getASTContext().getEntryPointFunctionName())
+    return false;
+
   // If this is for a declaration, ask it.
   if (auto declRef = getDeclRef()) {
     return declRef.hasNonUniqueDefinition();

test/embedded/linkage/diamond.swift

@@ -56,13 +56,12 @@
 // RUN: %target-run %t/Application | %FileCheck %s
 
 // Test #%: All "intermediate", all the time. Main drives code generation
-// TODO: @main needs to drive the generation of code here.
 // RUN: %target-swift-frontend -c -emit-module -o %t/Root.o %t/Root.swift -enable-experimental-feature Embedded -enable-experimental-feature DeferredCodeGen -parse-as-library
 // RUN: %target-swift-frontend -c -I %t -emit-module -o %t/ClientA.o %t/ClientA.swift -enable-experimental-feature Embedded -enable-experimental-feature DeferredCodeGen -parse-as-library
 // RUN: %target-swift-frontend -c -I %t -emit-module -o %t/ClientB.o %t/ClientB.swift -enable-experimental-feature Embedded -enable-experimental-feature DeferredCodeGen -parse-as-library
 // RUN: %target-swift-frontend -c -I %t -emit-module -o %t/Application.o %t/Application.swift -enable-experimental-feature Embedded -enable-experimental-feature DeferredCodeGen -parse-as-library
-// RUN-TODO: %target-clang %target-clang-resource-dir-opt %t/Root.o %t/ClientA.o %t/ClientB.o %t/Application.o -o %t/Application
-// RUN-TODO: %target-run %t/Application | %FileCheck %s
+// RUN: %target-clang %target-clang-resource-dir-opt %t/Root.o %t/ClientA.o %t/ClientB.o %t/Application.o -o %t/Application
+// RUN: %target-run %t/Application | %FileCheck %s
 
 
 // REQUIRES: swift_in_compiler