+(*) bootstrap.sh prints lots of warning something like this:
+------------------------------------------------------------
+autoreconf: running: aclocal --force -I m4
+configure.ac:47: warning: AC_COMPILE_IFELSE was called \
+before AC_USE_SYSTEM_EXTENSIONS
+../../lib/autoconf/specific.m4:389: AC_USE_SYSTEM_EXTENSIONS is expanded from...
+m4/lock.m4:29: gl_LOCK_EARLY_BODY is expanded from...
+m4/lock.m4:22: gl_LOCK_EARLY is expanded from...
+m4/lock.m4:253: gl_LOCK is expanded from...
+m4/intl.m4:186: gt_INTL_SUBDIR_CORE is expanded from...
+m4/intl.m4:25: AM_INTL_SUBDIR is expanded from...
+m4/gettext.m4:57: AM_GNU_GETTEXT is expanded from...
+configure.ac:47: the top level
+------------------------------------------------------------
+but, it seems that they can be just ignored.
+