Enable R8 full mode for system_server

This is the default for all app targets. Incrementally enable for
select library targets that are already being shrunk or optimized w/ R8
in anticipation of a broader default rollout for any optimized target.

Bug: 215530220
Test: m + presubmit
Change-Id: I17781fa5fa27f453694fbdd20e11f7ce387dede7
diff --git a/services/Android.bp b/services/Android.bp
index 3a0428e..0f6b984 100644
--- a/services/Android.bp
+++ b/services/Android.bp
@@ -58,6 +58,7 @@
                 optimize: false,
                 shrink: true,
                 ignore_warnings: false,
+                proguard_compatibility: false,
                 proguard_flags_files: [
                     "proguard.flags",
                     // Ensure classes referenced in the framework-res manifest