[gtk-vnc] meson: set _FORTIFY_SOURCE in config.h

[Daniel P. Berrange <dberrange src gnome org>]

commit 5f1dd669437802308579e72c3a49f1e84232f866
Author: Daniel P. Berrangé <dan berrange com>
Date:   Wed Mar 31 14:28:55 2021 +0100

    meson: set _FORTIFY_SOURCE in config.h
    
    Avoiding setting it in meson.build means we can honour the optimization
    level defined by meson.
    
    Signed-off-by: Daniel P. Berrangé <berrange redhat com>

 config.h.in | 7 +++++++
 meson.build | 2 --
 2 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/config.h.in b/config.h.in
index 3edbbdf..e75db04 100644
--- a/config.h.in
+++ b/config.h.in
@@ -1,4 +1,11 @@
 
+/* Enable compile-time and run-time bounds-checking, and some warnings,
+ * without upsetting newer glibc. */
+
+#if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
+# define _FORTIFY_SOURCE 2
+#endif
+
 /* Whether GIO UNIX is available */
 #mesondefine HAVE_GIOUNIX
 
diff --git a/meson.build b/meson.build
index 22c95dd..ef8bc66 100644
--- a/meson.build
+++ b/meson.build
@@ -232,8 +232,6 @@ check_cflags = [
   '-Wno-cast-function-type',
   '-Wjump-misses-init',
   '-Wframe-larger-than=40096',
-  '-O2',
-  '-Wp,-D_FORTIFY_SOURCE=2',
   '-fexceptions',
   '-fasynchronous-unwind-tables',
   '-fdiagnostics-show-option',