Bootstrapping offers options from the ${CMAKE_SOURCE_DIR}/bootstrap/ directory. Collect them all. Try to find the possible Debian systems as separate options.
Let the symlink just be one of the bootstrapping options (scan documentation for remarks about that too).
Most of the times, a single bootstrap option is selected. This can then be automatically selected (when no setting was made yet).
When multiple options are available, setup a bootstrap menu (including the symbolic link option). Deselect the current ${BUILDROOT_MKHERE} selection if it is not contained in the bootstrap menu.
When no options are available, switch to manual, but then require it having been setup, or fail.
After selection, check the presence of ${BUILDROOT_MKHERE}/lib/stdlib as a sanity check.
Continue to work with ${BUILDROOT_MKHERE} in the files CMakeLists.txt, as we do now.
${CMAKE_SOURCE_DIR}/bootstrap/directory. Collect them all. Try to find the possible Debian systems as separate options.${BUILDROOT_MKHERE}selection if it is not contained in the bootstrap menu.${BUILDROOT_MKHERE}/lib/stdlibas a sanity check.${BUILDROOT_MKHERE}in the filesCMakeLists.txt, as we do now.