Features: Test cycle diagnostic 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 cyclic requirement of a feature requiring
C++ 11, use the `std_cxx_11` meta-feature that has exactly this meaning.

Tests/RunCMake/CompileFeatures/LinkImplementationFeatureCycle.cmake

@@ -3,13 +3,13 @@ add_library(empty1 empty.cpp)
 
 add_library(empty2 INTERFACE)
 add_library(empty3 INTERFACE)
-target_compile_features(empty3 INTERFACE cxx_static_assert)
+target_compile_features(empty3 INTERFACE cxx_std_11)
 
 target_link_libraries(empty1
   # When starting, $<COMPILE_FEATURES:cxx_auto_type> is '0', so 'freeze' the
   # CXX_STANDARD at 98 during computation.
   $<$<COMPILE_FEATURES:cxx_auto_type>:empty2>
-  # This would add cxx_static_assert, but that would require CXX_STANDARD = 11,
+  # This would add cxx_std_11, but that would require CXX_STANDARD = 11,
   # which is not allowed after freeze.  Report an error.
   empty3
 )

Tests/RunCMake/CompileFeatures/LinkImplementationFeatureCycleSolved.cmake

@@ -3,7 +3,7 @@ add_library(empty1 empty.cpp)
 
 add_library(empty2 INTERFACE)
 add_library(empty3 INTERFACE)
-target_compile_features(empty3 INTERFACE cxx_static_assert)
+target_compile_features(empty3 INTERFACE cxx_std_11)
 
 target_link_libraries(empty1
   $<$<COMPILE_FEATURES:cxx_nullptr>:empty2>