[macos] Disable automatic signing management (#179)

Disable Xcode's default of automatically managing signing for the
example application, as this can cause issues for people who have a
developer team configured in Xcode.

Should address issue #178

Author: stuartmorgan

example/macos/ExampleEmbedder.xcodeproj/project.pbxproj

@@ -254,7 +254,7 @@
 					33CC10EC2044A3C60003C045 = {
 						CreatedOnToolsVersion = 9.2;
 						LastSwiftMigration = 0920;
-						ProvisioningStyle = Automatic;
+						ProvisioningStyle = Manual;
 					};
 					33CC111A2044C6BA0003C045 = {
 						CreatedOnToolsVersion = 9.2;
@@ -526,12 +526,14 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CLANG_ENABLE_MODULES = YES;
-				CODE_SIGN_STYLE = Automatic;
+				CODE_SIGN_STYLE = Manual;
 				COMBINE_HIDPI_IMAGES = YES;
+				DEVELOPMENT_TEAM = "";
 				INFOPLIST_FILE = Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.FlutterEmbedderMacExample.Example-Embedder";
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE_SPECIFIER = "";
 				SWIFT_OBJC_BRIDGING_HEADER = "Example Embedder-Bridging-Header.h";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 				SWIFT_VERSION = 4.0;
@@ -543,12 +545,14 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CLANG_ENABLE_MODULES = YES;
-				CODE_SIGN_STYLE = Automatic;
+				CODE_SIGN_STYLE = Manual;
 				COMBINE_HIDPI_IMAGES = YES;
+				DEVELOPMENT_TEAM = "";
 				INFOPLIST_FILE = Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.FlutterEmbedderMacExample.Example-Embedder";
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE_SPECIFIER = "";
 				SWIFT_OBJC_BRIDGING_HEADER = "Example Embedder-Bridging-Header.h";
 				SWIFT_VERSION = 4.0;
 			};