CPack: extend testing framework

Some CPack tests require running
commands after the inclusion of
CPack.cmake and this patch enables
such tests to declare run_after_include_cpack
function which is run after the
inclusion.

Tests/RunCMake/CPack/CMakeLists.txt

@@ -15,3 +15,7 @@ include(tests/${RunCMake_TEST_FILE_PREFIX}/test.cmake)
 
 set(CPACK_GENERATOR "${GENERATOR_TYPE}")
 include(CPack)
+
+if(COMMAND run_after_include_cpack)
+  run_after_include_cpack()
+endif()

Tests/RunCMake/CPack/README.txt

@@ -91,6 +91,11 @@ If test will be used for multiple generators but some of them require some
 generator specific commands then those commands should be added to 'test.cmake'
 script wrapped with 'if(GENERATOR_TYPE STREQUAL <name_of_the_generator>)'.
 
+NOTE: In some cases (for example when testing CPackComponent.cmake functions)
+the test has to run some functions after CPack.cmake is included. In such cases
+a function run_after_include_cpack can be declared in test.cmake file and that
+function will run after the inclusion of CPack.cmake.
+
 build phase (optional and not available for source package tests)
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