Supress a build warning.

-Wdeprecated-copy is enabled in ANGLE so supress it upstream in VMA.

Bug: angleproject:6343

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 8507ff7..e8e4d78 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -12,6 +12,7 @@
   include_dirs = [ "include" ]
   if (is_clang) {
     cflags_cc = [
+      "-Wno-deprecated-copy",
       "-Wno-implicit-fallthrough",
       "-Wno-nullability-completeness",
       "-Wno-suggest-destructor-override",