Build: configure: Use AC_SEARCH_LIBS for basic libraries.

* Get rid of the check for getopt_long, which is no longer used
  anywhere.

* Use AC_SEARCH_LIBS for finding libdl, but because that macro always
  adds the result of the test to $LIBS, we have to use a trick: save
  $LIBS, search for libdl, set $DL_LIBS to the result, and then restore
  $LIBS.

* Change LIBADD_DL to DL_LIBS for future consistency.

* Get rid of the "Where is dlopen?" block.  I think AC_SEARCH_LIBS makes
  this unnecessary.

* libcrmcommon links against socket and is used by everything, so we can
  just simply call AC_SEARCH_LIBS for it.

Related T876

configure.ac

@@ -1007,11 +1007,17 @@ AC_SUBST([GETOPT_PATH])
 dnl ===============================================
 dnl Libraries
 dnl ===============================================
-AC_CHECK_LIB(socket, socket)                    dnl -lsocket
-AC_CHECK_LIB(c, dlopen)                         dnl if dlopen is in libc...
-AC_CHECK_LIB(dl, dlopen)                        dnl -ldl (for Linux)
+AC_SEARCH_LIBS([socket], [socket])
+
+save_LIBS="$LIBS"
+DL_LIBS=""
+LIBS=""
+AC_SEARCH_LIBS([dlopen], [dl],
+               [test "$ac_cv_search_dlopen" = "none required" || DL_LIBS="$LIBS"])
+AC_SUBST(DL_LIBS)
+LIBS="$save_LIBS"
+
 AC_CHECK_LIB(rt, sched_getscheduler)            dnl -lrt (for Tru64)
-AC_CHECK_LIB(gnugetopt, getopt_long)            dnl -lgnugetopt ( if available )
 AC_CHECK_LIB(pam, pam_start)                    dnl -lpam (if available)
 
 PKG_CHECK_MODULES([UUID], [uuid],
@@ -1032,15 +1038,6 @@ PKG_CHECK_MODULES([GLIB], [glib-2.0 >= 2.42.0],
 # Check whether high-resolution sleep function is available
 AC_CHECK_FUNCS([nanosleep usleep])
 
-#
-# Where is dlopen?
-#
-AS_IF([test x"$ac_cv_lib_c_dlopen" = x"yes"],
-      [LIBADD_DL=""],
-      [test x"$ac_cv_lib_dl_dlopen" = x"yes"],
-      [LIBADD_DL=-ldl],
-      [LIBADD_DL=${lt_cv_dlopen_libs}])
-
 PKG_CHECK_MODULES(LIBXML2, [libxml-2.0 >= 2.9.2],
                   [CPPFLAGS="${CPPFLAGS} ${LIBXML2_CFLAGS}"
                    LIBS="${LIBS} ${LIBXML2_LIBS}"])

lib/common/Makefile.am

@@ -35,15 +35,13 @@ libcrmcommon_la_LDFLAGS	= -version-info 47:1:13
 libcrmcommon_la_CFLAGS	= $(CFLAGS_HARDENED_LIB)
 libcrmcommon_la_LDFLAGS	+= $(LDFLAGS_HARDENED_LIB)
 
-libcrmcommon_la_LIBADD = @LIBADD_DL@
-
 # If configured with --with-profiling or --with-coverage, BUILD_PROFILING will
 # be set and -fno-builtin will be added to the CFLAGS.  However, libcrmcommon
 # uses the fabs() function which is normally supplied by gcc as one of its
 # builtins.  Therefore we need to explicitly link against libm here or the
 # tests won't link.
 if BUILD_PROFILING
-libcrmcommon_la_LIBADD	+= -lm
+libcrmcommon_la_LIBADD	= -lm
 endif
 
 ## Library sources (*must* use += format for bumplibs)

lib/fencing/Makefile.am

@@ -21,6 +21,7 @@ libstonithd_la_LDFLAGS	+= $(LDFLAGS_HARDENED_LIB)
 
 libstonithd_la_LIBADD = $(top_builddir)/lib/services/libcrmservice.la
 libstonithd_la_LIBADD += $(top_builddir)/lib/common/libcrmcommon.la
+libstonithd_la_LIBADD += @DL_LIBS@
 
 ## Library sources (*must* use += format for bumplibs)
 libstonithd_la_SOURCES	= st_actions.c

lib/pacemaker-fencing.pc.in

@@ -11,4 +11,4 @@ Requires.private: glib-2.0 libxml-2.0
 Conflicts:
 Cflags:           -I${includedir}
 Libs:             -L${libdir} -l${sub}
-Libs.private:
+Libs.private:     @DL_LIBS@

lib/pacemaker.pc.in

@@ -29,4 +29,4 @@ Requires.private: glib-2.0 libxslt libxml-2.0 uuid gnutls
 Conflicts:
 Cflags:           -I${includedir}
 Libs:             -L${libdir} -l${sub}
-Libs.private:     @LIBADD_DL@ -lbz2
+Libs.private:     -lbz2