dist: correct sense of no-dist-built-sources option. Primarily from https://bugs.gnu.org/69908. * bin/automake.in (preprocess_file) <DIST_BUILT_SOURCES>: make the option name be "no-dist-built-sources", per Options.pm and automake.texi; then set it with a single !. * lib/am/distdir.am (distdir) [DIST_BUILT_SOURCES]: insert the dependency on $(BUILT_SOURCES) when DIST_BUILT_SOURCES is true, not false; i.e., sense was reversed. * t/dist-no-built-sources.sh: edit the test configure.ac in the no-dist-built-sources case. Rename the testopt value to match the Automake option. * NEWS: mention this.