Tests: Skip RunCMake.XcodeProject device cases for Xcode "new build system"

The Xcode "new build system" selects different architectures for device
builds than the old build system does.  Skip those tests on Xcode 12+
pending further investigation.

Issue: #21206

Tests/RunCMake/XcodeProject/RunCMakeTest.cmake

@@ -108,6 +108,11 @@ XcodeRemoveExcessiveISystem()
 # Isolate device tests from host architecture selection.
 unset(ENV{CMAKE_OSX_ARCHITECTURES})
 
+if(XCODE_VERSION VERSION_GREATER_EQUAL 12)
+  # FIXME: Restore device tests and fix them for the Xcode "new build system"
+  return()
+endif()
+
 # Use a single build tree for a few tests without cleaning.
 
 if(NOT XCODE_VERSION VERSION_LESS 5)