Avoid calls to the undeclared strlcpy function in libsync.  This
prevents a build failure with future compilers.

Submitted upstream: <https://bugreports.qt.io/browse/QTBUG-111440>

diff -up qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/BUILD.gn.c99 qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/BUILD.gn
--- qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/BUILD.gn.c99	2023-02-23 10:54:15.909380015 +0100
+++ qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/BUILD.gn	2023-02-23 11:00:32.019601795 +0100
@@ -21,24 +21,15 @@ if (!use_system_libsync) {
     ]
   }
 
-  config("libsync_private_config") {
-    # To suppress the warning caused by strlcpy.
-    cflags = [ "-Wno-implicit-function-declaration" ]
-  }
-
   source_set("libsync") {
     sources = [
       "src/include/sync/sync.h",
       "src/sw_sync.h",
       "src/sync.c",
-      "strlcpy.c",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
-    configs += [
-      "//build/config/compiler:no_chromium_code",
-      ":libsync_private_config",
-    ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":libsync_config" ]
   }
diff -up qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/src/sync.c.c99 qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/src/sync.c
--- qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/src/sync.c.c99	2023-02-23 10:54:30.650231820 +0100
+++ qtwebengine-everywhere-src-5.15.12/src/3rdparty/chromium/third_party/libsync/src/sync.c	2023-02-23 10:54:50.116036131 +0100
@@ -29,6 +29,7 @@
 
 #include <sync/sync.h>
 
+#include "../strlcpy.c"
 
 struct sw_sync_create_fence_data {
   __u32 value;