[roottest[ fully dismiss RootExternalIncludes

Replaced by ROOTEXE_OPTS argument which
is individual for each test and does not interfere with other tests

Author: linev

roottest/cmake/modules/RoottestMacros.cmake

@@ -687,7 +687,7 @@ macro(ROOTTEST_SETUP_MACROTEST)
                -e "gROOT->SetMacroPath(\"${CMAKE_CURRENT_SOURCE_DIR}\")"
                -e "gInterpreter->AddIncludePath(\"-I${CMAKE_CURRENT_BINARY_DIR}\")"
                -e "gSystem->AddIncludePath(\"-I${CMAKE_CURRENT_BINARY_DIR}\")"
-               ${RootExternalIncludes} ${ARG_ROOTEXE_OPTS}
+               ${ARG_ROOTEXE_OPTS}
                -q -l -b)
 
   set(root_buildcmd ${ROOT_root_CMD} ${RootExeDefines} -q -l -b)