Allow reordered MAKEFLAGS

-R and -r (-Rr) can be reordered to -r and -R (-rR).
This happens with MSYS1/2 gnu-make and mingw32-make,
and triggers "Recursion detected, bailing out..."

Signed-off-by: Ray Donnelly <mingw.android@gmail.com>
Message-Id: <CAOYw7dsdsg-XaDOwwEWJeUUSo2Vu_UD5GtkSgNTu59ai7yx0cQ@mail.gmail.com>
Patchwork-Id: 258027

 # Compute s390-specific values

 CT_DoArchTupleValues() {

     # That's the only thing to override

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="s390x${CT_ARCH_SUFFIX}"

     fi

 }