Currently, the makefile fails catastrophically if the build directory contains
spaces or quotes, so we better detect them early.

Otherwise configure won't bother with giving a value to the appropriate
variables...

`configure_tool` performs everything by itself.

turns out `m4_index` treats its first argument as one big string and not a
sequence of words. `m4_regexp` with words delimiters in the regexp is thus
better suited for the task.

Andre Maroneze authored 5 years ago and Virgile Prevosto committed 5 years ago

Thanks to madroach for spotting the issue and providing a patch.

       because always true now

(blind make headers from specifications)