m4

Prepare

./bootstrap --force --skip-git --skip-po is broken as of 1.4.20 along with autoreconf
Depends on gperf, help2man, mawk and itself

changeword is experimental and disabled by default as it degrades performance
m4 uses bundled gnulib and it can’t be disabled (--without-gnulib does not exist)
--without-gnulib-prefix prevents searching for an external gnulib
--without-included-regex breaks build as m4 uses gnu extensions like re_compile_pattern, re_search and re_set_registers
m4 is single-threaded and gnulib is optimized for that (gl_DISABLE_THREADS) still passing --enable-threads=posix does not hurt
No need to pass --without-libsigsegv-prefix if --without-libsigsegv is set