Use monotonic raw timestamp by default except for x86/64

chromecast/media/cma/backend/alsa/BUILD.gn

Index: chromecast/media/cma/backend/alsa/BUILD.gn
diff --git a/chromecast/media/cma/backend/alsa/BUILD.gn b/chromecast/media/cma/backend/alsa/BUILD.gn
index c12367d8a9be472b2ef6d5c77ce0d89a342d24d5..04e21d664ea8f5da0f240046b3a73d858abafe92 100644
--- a/chromecast/media/cma/backend/alsa/BUILD.gn
+++ b/chromecast/media/cma/backend/alsa/BUILD.gn
@@ -3,13 +3,14 @@
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
+import("//build/config/chromecast_build.gni")
 import("//media/media_options.gni")
 import("//testing/test.gni")
 
 declare_args() {
-  # Set true to use raw timestamps. This should only be enabled when the ALSA
-  # library supports it.
-  use_alsa_monotonic_raw_tstamps = false
+  # Set true to use raw timestamps on non-desktop cast build.
+  # ALSA version equal or later than 1.0.29 support this function.
+  use_alsa_monotonic_raw_tstamps = !is_cast_desktop_build
 }
 
 # Alsa must be used for these targets to build.