Disable code signing in generated Xcode project

Since code signing is done as part of the build (via create_bundle),
the generated project must disable the code signing otherwise Xcode
complains.

This is done by configuring an empty code signing identity.

Bug: none
Change-Id: Ifee80ee45659da833380f0b47c58782a6c08ccf3
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/9001
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>

src/gn/xcode_object.cc

diff --git a/src/gn/xcode_object.cc b/src/gn/xcode_object.cc
index 471a201..7948b17 100644
--- a/src/gn/xcode_object.cc
+++ b/src/gn/xcode_object.cc
@@ -812,7 +812,7 @@
                                     const std::string& shell_script) {
   PBXAttributes attributes;
   attributes["CLANG_ENABLE_OBJC_WEAK"] = "YES";
-  attributes["CODE_SIGN_IDENTITY"] = "-";
+  attributes["CODE_SIGN_IDENTITY"] = "";
   attributes["CODE_SIGNING_REQUIRED"] = "NO";
   attributes["CONFIGURATION_BUILD_DIR"] = ".";
   attributes["PRODUCT_NAME"] = name;
@@ -825,7 +825,7 @@
   DCHECK(!target_for_indexing_);
   PBXAttributes attributes;
   attributes["CLANG_ENABLE_OBJC_WEAK"] = "YES";
-  attributes["CODE_SIGN_IDENTITY"] = "-";
+  attributes["CODE_SIGN_IDENTITY"] = "";
   attributes["CODE_SIGNING_REQUIRED"] = "NO";
   attributes["EXECUTABLE_PREFIX"] = "";
   attributes["HEADER_SEARCH_PATHS"] = sources_->path();
@@ -869,7 +869,7 @@
 
   PBXAttributes attributes = extra_attributes;
   attributes["CLANG_ENABLE_OBJC_WEAK"] = "YES";
-  attributes["CODE_SIGN_IDENTITY"] = "-";
+  attributes["CODE_SIGN_IDENTITY"] = "";
   attributes["CODE_SIGNING_REQUIRED"] = "NO";
   attributes["CONFIGURATION_BUILD_DIR"] = output_dir;
   attributes["PRODUCT_NAME"] = product_name;