Use ac_save_LIBS instead of LIBS_OLD

configure.ac

@@ -268,9 +268,9 @@ if test "x${have_zlib}" = "xno"; then
 fi
 
 # dl: openssl requires libdl when it is statically linked.
-LIBS_OLD=$LIBS
+ac_save_LIBS=$LIBS
 AC_SEARCH_LIBS([dlopen], [dl], [APPLDFLAGS="-ldl $APPLDFLAGS"], [], [])
-LIBS=$LIBS_OLD
+LIBS=$ac_save_LIBS
 
 # cunit
 PKG_CHECK_MODULES([CUNIT], [cunit >= 2.1], [have_cunit=yes], [have_cunit=no])
@@ -303,7 +303,7 @@ AM_CONDITIONAL([HAVE_CUNIT], [ test "x${have_cunit}" = "xyes" ])
 
 # libev (for src)
 # libev does not have pkg-config file.  Check it in an old way.
-LIBS_OLD=$LIBS
+ac_save_LIBS=$LIBS
 # android requires -lm for floor
 AC_CHECK_LIB([ev], [ev_time], [have_libev=yes], [have_libev=no], [-lm])
 if test "x${have_libev}" = "xyes"; then
@@ -315,7 +315,7 @@ if test "x${have_libev}" = "xyes"; then
     AC_SUBST([LIBEV_CFLAGS])
   fi
 fi
-LIBS=$LIBS_OLD
+LIBS=$ac_save_LIBS
 
 # openssl (for src)
 PKG_CHECK_MODULES([OPENSSL], [openssl >= 1.0.1],
@@ -361,7 +361,7 @@ AM_CONDITIONAL([HAVE_LIBXML2], [ test "x${have_libxml2}" = "xyes" ])
 # jemalloc
 have_jemalloc=no
 if test "x${request_jemalloc}" != "xno"; then
-  LIBS_OLD=$LIBS
+  ac_save_LIBS=$LIBS
   AC_SEARCH_LIBS([malloc_stats_print], [jemalloc], [have_jemalloc=yes], [],
                  [$PTHREAD_LDFLAGS])
 
@@ -377,7 +377,7 @@ if test "x${request_jemalloc}" != "xno"; then
     fi
   fi
 
-  LIBS=$LIBS_OLD
+  LIBS=$ac_save_LIBS
 
   if test "x${have_jemalloc}" = "xyes" &&
      test "x${jemalloc_libs}" != "xnone required"; then