configure.ac:

AC_ARG_WITH(locker,
AC_HELP_STRING(--without-locker,[Disable locker support]),
locker=$withval,
locker=yes)

AM_CONDITIONAL([BUILD_LOCKER_COMPONENTS], [test x$locker = xyes])


Makefile.am:

if BUILD_LOCKER_COMPONENTS
        LOCKER_EXAMPLE = example_locker
else
        LOCKER_EXAMPLE =
endif

noinst_PROGRAMS = $(LOCKER_EXAMPLE)