configure: Replace broken AM_PROG_LEX with AC_CHECK_PROGS
configure: Replace broken AM_PROG_LEX with AC_CHECK_PROGS

Signed-off-by: Thomas Graf <17c2d8920621522552b392f72d8fdb4d1e866b44@suug.ch>

karlhiramoto/libnl,houstar/libnl,chitranshi/libnl,cyclops8456/libnl3,teto/libnl_old,cfriedt/libnl,tklauser/libnl,baloo/libnl,houstar/libnl,UnicronNL/libnl3,tgraf/libnl,teto/libnl_old,kolyshkin/libnl,congwang/libnl,dsahern/libnl,cfriedt/libnl,houstar/libnl,greearb/libnl-ct,claudelee/libnl,vyos/libnl3,teto/libnl_old,tgraf/libnl,mshirley/libnl,UnicronNL/libnl3,kolyshkin/libnl,tklauser/libnl,vyos/libnl3,claudelee/libnl,congwang/libnl,mshirley/libnl,vyos/libnl3,dsahern/libnl,chitranshi/libnl,vyos/libnl3,congwang/libnl,baloo/libnl,HolyShitMan/libnl-1,tgraf/libnl,dsahern/libnl,Distrotech/libnl,tgraf/libnl,mshirley/libnl,HolyShitMan/libnl-1,thom311/libnl,claudelee/libnl,claudelee/libnl,houstar/libnl,karlhiramoto/libnl,greearb/libnl-ct,cyclops8456/libnl3,HolyShitMan/libnl-1,mshirley/libnl,Distrotech/libnl,baloo/libnl,karlhiramoto/libnl,congwang/libnl,kolyshkin/libnl,UnicronNL/libnl3,honsys/libnl,Distrotech/libnl,Distrotech/libnl,karlhiramoto/libnl,thom311/libnl,tklauser/libnl,cyclops8456/libnl3,teto/libnl_old,cfriedt/libnl,HolyShitMan/libnl-1,thom311/libnl,baloo/libnl,UnicronNL/libnl3,cyclops8456/libnl3,tklauser/libnl,cfriedt/libnl,kolyshkin/libnl,chitranshi/libnl,honsys/libnl,chitranshi/libnl,honsys/libnl,dsahern/libnl,greearb/libnl-ct,honsys/libnl