Tests: Improve RunCMake.GetPrerequisites sample executable selection

Get the runtime dependencies of an executable just built by the
toolchain with which tests are running.  Previously we used the `cmake`
binary itself, but that might have been built for a different ABI than
the tested binutils support.

Tests/RunCMake/CMakeLists.txt

@@ -361,7 +361,7 @@ if(XCODE_VERSION)
   set(GeneratorToolset_ARGS -DXCODE_VERSION=${XCODE_VERSION})
 endif()
 add_RunCMake_test(GeneratorToolset)
-add_RunCMake_test(GetPrerequisites)
+add_RunCMake_test(GetPrerequisites -DSAMPLE_EXE=$<TARGET_FILE:exit_code>)
 add_RunCMake_test(GNUInstallDirs -DSYSTEM_NAME=${CMAKE_SYSTEM_NAME})
 add_RunCMake_test(GoogleTest) # Note: does not actually depend on Google Test
 add_RunCMake_test(Graphviz)

Tests/RunCMake/GetPrerequisites/ExecutableScripts.cmake

@@ -10,7 +10,9 @@ endfunction()
 
 # Should not throw any errors
 # Regular executable
-get_prerequisites(${CMAKE_COMMAND} cmake_prereqs 1 1 "" "")
+if(SAMPLE_EXE)
+  get_prerequisites("${SAMPLE_EXE}" cmake_prereqs 1 1 "" "")
+endif()
 # Shell script
 check_script(${CMAKE_CURRENT_LIST_DIR}/script.sh)
 # Batch script

Tests/RunCMake/GetPrerequisites/RunCMakeTest.cmake

@@ -1,4 +1,4 @@
 include(RunCMake)
 
 run_cmake_command(TargetMissing ${CMAKE_COMMAND} -P ${RunCMake_SOURCE_DIR}/TargetMissing.cmake)
-run_cmake_command(ExecutableScripts ${CMAKE_COMMAND} -P ${RunCMake_SOURCE_DIR}/ExecutableScripts.cmake)
+run_cmake_command(ExecutableScripts ${CMAKE_COMMAND} -DSAMPLE_EXE=${SAMPLE_EXE} -P ${RunCMake_SOURCE_DIR}/ExecutableScripts.cmake)