Tests: Tell Xcode to disallow signing altogether in relevant cases

The Xcode 'new build system' rejects empty signing identities unless
signing is explicitly marked as not allowed.  Update test cases where we
turn off signing to explicitly disallow it too.

Also turn off signing in the XCTest test.

Tests/RunCMake/XcodeProject/DeploymentTarget.cmake

@@ -5,15 +5,18 @@ project(DeploymentTarget C)
 
 if(CMAKE_SYSTEM_NAME STREQUAL "iOS")
   set(CMAKE_OSX_DEPLOYMENT_TARGET "9.1")
+  set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_ENABLE_BITCODE "NO")
 elseif(CMAKE_SYSTEM_NAME STREQUAL "watchOS")
   set(CMAKE_OSX_DEPLOYMENT_TARGET "2.0")
+  set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
   set(CMAKE_XCODE_ATTRIBUTE_ENABLE_BITCODE "YES")
 elseif(CMAKE_SYSTEM_NAME STREQUAL "tvOS")
   set(CMAKE_OSX_DEPLOYMENT_TARGET "9.0")
+  set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
   set(CMAKE_XCODE_ATTRIBUTE_ENABLE_BITCODE "YES")

Tests/RunCMake/XcodeProject/XcodeBundles.cmake

@@ -4,12 +4,14 @@ cmake_minimum_required(VERSION 3.3)
 enable_language(C)
 
 if(CMAKE_SYSTEM_NAME STREQUAL "iOS")
+  set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
   set(CMAKE_XCODE_ATTRIBUTE_ENABLE_BITCODE "NO")
 endif()
 
 if(CMAKE_SYSTEM_NAME STREQUAL "tvOS" OR CMAKE_SYSTEM_NAME STREQUAL "watchOS")
+  set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
   set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
   set(CMAKE_XCODE_ATTRIBUTE_ENABLE_BITCODE "YES")

Tests/RunCMake/XcodeProject/XcodeIOSInstallCombined.cmake

@@ -10,6 +10,7 @@ if(NOT IOS)
   message(FATAL_ERROR "IOS variable is not set")
 endif()
 
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
 set(CMAKE_XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT "dwarf")

Tests/RunCMake/XcodeProject/XcodeIOSInstallCombinedPrune.cmake

@@ -6,6 +6,7 @@ if(XCODE_VERSION VERSION_GREATER_EQUAL 9)
   set(CMAKE_OSX_DEPLOYMENT_TARGET 10)
 endif()
 
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
 set(CMAKE_XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT "dwarf")

Tests/RunCMake/XcodeProject/XcodeIOSInstallCombinedSingleArch.cmake

@@ -6,6 +6,7 @@ if(XCODE_VERSION VERSION_GREATER_EQUAL 9)
   set(CMAKE_OSX_DEPLOYMENT_TARGET 10)
 endif()
 
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
 set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
 set(CMAKE_XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT "dwarf")

Tests/XCTest/CMakeLists.txt

@@ -2,6 +2,10 @@ cmake_minimum_required(VERSION 3.1)
 project(XCTest C)
 enable_testing()
 
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_REQUIRED "NO")
+set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "")
+
 find_package(XCTest REQUIRED)
 
 # Framework