I've just cloned Emacs from git ant tried to build Emacs on GNU Linux (Debian 9), but the configure script is missing.

So, I tried to generate via autoconf, but I got the following error:

configure.ac:54: error: possibly undefined macro: AS_ECHO
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
configure.ac:1695: error: possibly undefined macro: m4_default

Am I missing something?