build: resolve automake-1.12 warnings
build: resolve automake-1.12 warnings

am/ltlibrary.am: warning: 'libnetfilter_acct.la': linking libtool
libraries using a non-POSIX archiver requires 'AM_PROG_AR' in
'configure.ac'

Signed-off-by: Jan Engelhardt <f383ed465f890d2e8ea864dd0c28cf8ec50a8942@inai.de>

Distrotech/libnetfilter_acct,Distrotech/libnetfilter_acct