sci-physics/root: Remove header expansion logic from RootNewMacros.cmake.

sci-physics/root: Remove header expansion logic from RootNewMacros.cmake.

  The fancy path expansion is not needed for Gentoo and actually
  causes runtime bugs, like

  Error in cling::AutoloadingVisitor::InsertIntoAutoloadingState:
    Missing FileEntry for /var/tmp/portage/sci-physics/JSAP-479/work/JSAP-479/DataType/JPSimOutput.hh
    requested to autoload type JPSimTriggerInfoTree_t

  portage automatically removes PORTAGE_TMPDIR from rpath ELF fields.
  The same applies to rootcling headers.

Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Benda Xu <heroxbd@gentoo.org>