Break crashpad_handler into lib and exe for Windows

handler/main.cc

Index: handler/main.cc
diff --git a/handler/main.cc b/handler/main.cc
index 0ec6e7f2148719ebdfc688d55ae674849d76f857..54254578cdcb8820c54362f324e13433857171ee 100644
--- a/handler/main.cc
+++ b/handler/main.cc
@@ -50,6 +50,7 @@
 #endif  // OS_MACOSX
 
 namespace crashpad {
+
 namespace {
 
 void Usage(const base::FilePath& me) {
@@ -77,6 +78,8 @@ void Usage(const base::FilePath& me) {
   ToolSupport::UsageTail(me);
 }
 
+}  // namespace
+
 int HandlerMain(int argc, char* argv[]) {
   const base::FilePath argv0(
       ToolSupport::CommandLineArgumentToFilePathStringType(argv[0]));
@@ -323,15 +326,4 @@ int HandlerMain(int argc, char* argv[]) {
   return EXIT_SUCCESS;
 }
 
-}  // namespace
 }  // namespace crashpad
-
-#if defined(OS_MACOSX)
-int main(int argc, char* argv[]) {
-  return crashpad::HandlerMain(argc, argv);
-}
-#elif defined(OS_WIN)
-int wmain(int argc, wchar_t* argv[]) {
-  return crashpad::ToolSupport::Wmain(argc, argv, crashpad::HandlerMain);
-}
-#endif  // OS_MACOSX