Append phpdbg CFLAGS in config.m4

Author: petk

sapi/phpdbg/config.m4

@@ -24,10 +24,10 @@ if test "$PHP_PHPDBG" != "no"; then
   AC_HEADER_TIOCGWINSZ
   AC_DEFINE(HAVE_PHPDBG, 1, [ ])
 
+  PHP_PHPDBG_CFLAGS="-DZEND_ENABLE_STATIC_TSRMLS_CACHE=1"
   AS_VAR_IF([PHP_PHPDBG_DEBUG], [no],,
-    [PHP_PHPDBG_CFLAGS="$PHP_PHPDBG_CFLAGS -DPHPDBG_DEBUG=1"])
+    [AS_VAR_APPEND([PHP_PHPDBG_CFLAGS], [" -DPHPDBG_DEBUG=1"])])
 
-  PHP_PHPDBG_CFLAGS="-DZEND_ENABLE_STATIC_TSRMLS_CACHE=1"
   PHP_PHPDBG_FILES="phpdbg.c phpdbg_parser.c phpdbg_lexer.c phpdbg_prompt.c phpdbg_help.c phpdbg_break.c phpdbg_print.c phpdbg_bp.c phpdbg_list.c phpdbg_utils.c phpdbg_info.c phpdbg_cmd.c phpdbg_set.c phpdbg_frame.c phpdbg_watch.c phpdbg_btree.c phpdbg_sigsafe.c phpdbg_io.c phpdbg_out.c"
 
   AC_MSG_CHECKING([for phpdbg and readline integration])