COMP: Update ITKModuleExternal CMake message to avoid CTest false pos…

…itive

This commit updates message introduced in 4b010e7 (ENH: use the new
CMake mechanism to specify MSVC's static or DLL CRT) to avoid false
positive when building module like ITKUltrasound as a standalone project.

Removing the "error" string avoid the regular expression associated
with cmCTestBuildHandler.cxx (see [1]) from reporting an error.

[1] https://github.com/Kitware/CMake/blob/7dc7907837a8ce4608f8cc762409617e62c496fe/Source/CTest/cmCTestBuildHandler.cxx#L28-L169

Co-authored-by: Connor Bowley <connor.bowley@kitware.com>
Co-authored-by: James Fishbaugh <james.fishbaugh@kitware.com>
Co-authored-by: Sam Horvath <sam.horvath@kitware.com>

CMake/ITKModuleExternal.cmake

@@ -12,7 +12,7 @@ if(MSVC AND ${CMAKE_MINIMUM_REQUIRED_VERSION} LESS 3.16.3)
   message(WARNING "cmake_minimum_required must be at least 3.16.3")
   message(STATUS "This is needed to allow proper setting of CMAKE_MSVC_RUNTIME_LIBRARY.")
   message(STATUS "Do not be surprised if you run into link errors of the style:
-  error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MTd_Static' doesn't match value 'MDd_Dynamic' in module.obj")
+  LNK2038: mismatch detected for 'RuntimeLibrary': value 'MTd_Static' doesn't match value 'MDd_Dynamic' in module.obj")
 endif()
 if(NOT EXISTS ${ITK_CMAKE_DIR}/ITKModuleMacros.cmake)
   message(FATAL_ERROR "Modules can only be built against an ITK build tree; they cannot be built against an ITK install tree.")