fix build.yaml to expand nanopb headers filegroup
diff --git a/package.xml b/package.xml
index d5bd4d0..9e23043 100644
--- a/package.xml
+++ b/package.xml
@@ -379,6 +379,10 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_common.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_decode.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_encode.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h" role="src" />