I'm trying to build upstream source on RHEL 7.5 and get this error:

# autoreconf -i

libtoolize: putting auxiliary files in `.'.

libtoolize: copying file `./ltmain.sh'

libtoolize: putting macros in AC_CONFIG_MACRO_DIR, `m4'.

libtoolize: copying file `m4/libtool.m4'

libtoolize: copying file `m4/ltoptions.m4'

libtoolize: copying file `m4/ltsugar.m4'

libtoolize: copying file `m4/ltversion.m4'

libtoolize: copying file `m4/lt~obsolete.m4'

configure.ac:190: error: possibly undefined macro: PKG_CHECK_VAR

      If this token and others are legitimate, please use m4_pattern_allow.

      See the Autoconf documentation.

autoreconf: /usr/bin/autoconf failed with exit status: 1

How to fix this? I hope I can avoid reading autoconf documentation :-)

Nir