Build libcodec2_client with gnu++20

Bug: http://b/343951602

Explicitly set cpp_std for libcodec2_client to gnu++20.  The default
inherited from libcodec2-impl-defaults sets it to gnu++17 which causes a
segfault when mixing global std::string symbols built with gnu++17 and
gnu++20.  Once the  libcodec2-impl-defaults setting to gnu++17 is
removed, this can be cleaned up.

Test: lunch aosp_cf_x86_64_phone-userdebug && m && acloud create with clang-r522817
Change-Id: I72991835a29ef923284e81fdf3c1dd28a6b99663
diff --git a/media/codec2/hal/client/Android.bp b/media/codec2/hal/client/Android.bp
index af6f4ae..864eeb8 100644
--- a/media/codec2/hal/client/Android.bp
+++ b/media/codec2/hal/client/Android.bp
@@ -33,6 +33,13 @@
         "libcodec2-aidl-client-defaults",
     ],
 
+    // http://b/343951602#comment4 Explicitly set cpp_std to gnu++20.  The
+    // default inherited from libcodec2-impl-defaults sets it to gnu++17 which
+    // causes a segfault when mixing global std::string symbols built with
+    // gnu++17 and gnu++20.  TODO(b/343951602): clean this after
+    // libcodec2-impl-defaults opt into gnu++17 is removed.
+    cpp_std: "gnu++20",
+
     header_libs: [
         "libcodec2_internal", // private
     ],