You use an obsolete touch syntax in src/Makefile.in. Current GNU touch apparently won't recognize it unless _POSIX2_VERSION is set to 199209.
(For some reason, building 7.8.866 from exported source still works, but when I tried building 8.0.2 the same way (I used make snapshot_export), the rebuilding of interpret_functions.h failed since precompile.sh couldn't find pike, which shouldn't be surprising since it's not built yet at that point, is it?)
Do you know any relevant systems where the following, which is POSIX.1-2001, wouldn't work?
--- a/src/Makefile.in +++ b/src/Makefile.in @@ -1357,7 +1357,7 @@ precompile.sh: $(SRCDIR)/precompile.sh.i # recursive use of make. precompile.sh-stamp: @if [ -f precompile.sh ]; then :; else $(MAKE) precompile.sh; fi - @touch 0101010185 precompile.sh-stamp 2>/dev/null + @touch -t 198501010101 precompile.sh-stamp 2>/dev/null
$(SRCDIR)/machine.h.in: $(SRCDIR)/stamp-h.in @if test -f $(SRCDIR)/machine.h.in; then :; else \