Intel: Record support for relaxed constexpr by version 18.0.5

Update the special case added by commit f719a13c28 (Features: Add
special case to disable relaxed constexpr for Intel 18, 2018-06-04,
v3.12.0-rc1~11^2) to record that 18.0.5 fixed the regression.

Modules/Compiler/Intel-CXX-FeatureTests.cmake

@@ -24,7 +24,7 @@ set(DETECT_CXX14 "((__cplusplus >= 201300L) || ((__cplusplus == 201103L) && !def
 unset(DETECT_BUGGY_ICC15)
 
 set(Intel17_CXX14 "__INTEL_COMPILER >= 1700 && ${DETECT_CXX14}")
-set(_cmake_feature_test_cxx_relaxed_constexpr "__cpp_constexpr >= 201304 || (${Intel17_CXX14} && __INTEL_COMPILER != 1800 && !defined(_MSC_VER))")
+set(_cmake_feature_test_cxx_relaxed_constexpr "__cpp_constexpr >= 201304 || (${Intel17_CXX14} && !(__INTEL_COMPILER == 1800 && __INTEL_COMPILER_UPDATE < 5) && !defined(_MSC_VER))")
 
 set(Intel16_CXX14 "__INTEL_COMPILER >= 1600 && ${DETECT_CXX14}")
 set(_cmake_feature_test_cxx_aggregate_default_initializers "${Intel16_CXX14}")