“As of version 3.9.0 (2015-10-14), FTS5 is included as part of the SQLite amalgamation. It is disabled by default. If using the two autoconf build system, it is enabled by specifying the "--enable-fts5" option when running the configure script. ”.
sqlite-autoconf-3310100/configure --help prints:
--enable-fts5 include fts5 support [default=yes]
This is a contradiction as the default is both to include and to not include FTS5 support.
Moreover, for options enabled by default, ./configure --help shall print
--disable-abc Disalbe abc
and for options disabled by default, ./configure --help shall print
--enable-abc Enable abc
This saves writing [default=yes or no] and convinces to type only options that change default behaviour: like --disable-static-shell --enable-debug.