Features: Test feature propagation with language standard meta-feature

The `cxx_static_assert` feature may be available in C++ 98 mode of some
compilers or not available at all in others.  Intstead of using an
individual feature to test propagation of a feature requiring C++ 11,
use the `std_cxx_11` meta-feature that has exactly this meaning.

Tests/CompileFeatures/CMakeLists.txt

@@ -398,7 +398,7 @@ if (CMAKE_CXX_COMPILE_FEATURES)
   )
 
   add_executable(CompileFeaturesGenex2 genex_test.cpp)
-  target_compile_features(CompileFeaturesGenex2 PRIVATE cxx_static_assert)
+  target_compile_features(CompileFeaturesGenex2 PRIVATE cxx_std_11)
   target_compile_definitions(CompileFeaturesGenex2 PRIVATE
     HAVE_OVERRIDE_CONTROL=$<COMPILE_FEATURES:cxx_final,cxx_override>
     HAVE_AUTO_TYPE=$<COMPILE_FEATURES:cxx_auto_type>
@@ -407,10 +407,10 @@ if (CMAKE_CXX_COMPILE_FEATURES)
     HAVE_INHERITING_CONSTRUCTORS_AND_FINAL=$<COMPILE_FEATURES:cxx_inheriting_constructors,cxx_final>
   )
 
-  add_library(static_assert_iface INTERFACE)
-  target_compile_features(static_assert_iface INTERFACE cxx_static_assert)
+  add_library(std_11_iface INTERFACE)
+  target_compile_features(std_11_iface INTERFACE cxx_std_11)
   add_executable(CompileFeaturesGenex3 genex_test.cpp)
-  target_link_libraries(CompileFeaturesGenex3 PRIVATE static_assert_iface)
+  target_link_libraries(CompileFeaturesGenex3 PRIVATE std_11_iface)
   target_compile_definitions(CompileFeaturesGenex3 PRIVATE
     HAVE_OVERRIDE_CONTROL=$<COMPILE_FEATURES:cxx_final,cxx_override>
     HAVE_AUTO_TYPE=$<COMPILE_FEATURES:cxx_auto_type>