m4: '+=' is not universally supported

* m4/libtool.m4: Remove '+=' in variable assignment since it is not
  universally supported.

diff --git a/m4/libtool.m4 b/m4/libtool.m4
index 381d4cb3587fd7c6251462c57ff6b4aad5e75789..31f1be04ba653f68f4d532e573ed03b8ea056b3a 100644 (file)
--- a/m4/libtool.m4
+++ b/m4/libtool.m4
@@ -1030,7 +1030,7 @@ m4_defun_once([_LT_REQUIRED_DARWIN_CHECKS],[
     AC_CACHE_CHECK([for -no_fixup_chains linker flag],
       [lt_cv_support_no_fixup_chains],
       [ save_LDFLAGS=$LDFLAGS
-        LDFLAGS+=" -Wl,-no_fixup_chains"
+        LDFLAGS="$LDFLAGS -Wl,-no_fixup_chains"
         AC_LINK_IFELSE(
           [AC_LANG_PROGRAM([],[])],
           lt_cv_support_no_fixup_chains=yes,
@@ -1091,7 +1091,7 @@ _LT_EOF
         *)
           _lt_dar_allow_undefined='$wl-undefined ${wl}dynamic_lookup'
           if test yes = "$lt_cv_support_no_fixup_chains"; then
-            _lt_dar_allow_undefined+=' $wl-no_fixup_chains'
+            _lt_dar_allow_undefined='$_lt_dar_allow_undefined $wl-no_fixup_chains'
           fi
         ;;
       esac