GenerateExportHeader: Recognize Intel < 12 more strictly

Match exactly the `Intel` compiler id.

Signed-off-by: William R. Dieter <[email protected]>

Modules/GenerateExportHeader.cmake

@@ -221,7 +221,7 @@ macro(_test_compiler_hidden_visibility)
     set(GCC_TOO_OLD TRUE)
   elseif(CMAKE_COMPILER_IS_GNUCC AND CMAKE_C_COMPILER_VERSION VERSION_LESS "4.2")
     set(GCC_TOO_OLD TRUE)
-  elseif(CMAKE_CXX_COMPILER_ID MATCHES Intel AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "12.0")
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Intel" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "12.0")
     set(_INTEL_TOO_OLD TRUE)
   endif()