Generate rules.mk for flagset via cargo_embargo

Update cargo_embargo.json to also generate Trusty rules.mk for use
in the Trusty kernel.

Test: cargo_embargo generate cargo_embargo.json
Change-Id: Idb59b2c30c7d0e8ec94207b816c4339569224fc0
diff --git a/crates/flagset/cargo_embargo.json b/crates/flagset/cargo_embargo.json
index 69a8042..53500c0 100644
--- a/crates/flagset/cargo_embargo.json
+++ b/crates/flagset/cargo_embargo.json
@@ -24,6 +24,10 @@
           "no_std": true
         }
       }
+    },
+    {
+      "generate_androidbp": false,
+      "generate_rulesmk": true
     }
   ]
 }
diff --git a/crates/flagset/rules.mk b/crates/flagset/rules.mk
index 3dc41e6..4e3b902 100644
--- a/crates/flagset/rules.mk
+++ b/crates/flagset/rules.mk
@@ -1,14 +1,15 @@
-# This file is generated by cargo2rulesmk.py --run --features .
-# Do not modify this file as changes will be overridden on upgrade.
+# This file is generated by cargo_embargo.
+# Do not modify this file after the LOCAL_DIR line
+# because the changes will be overridden on upgrade.
+# Content before the first line starting with LOCAL_DIR is preserved.
 
 LOCAL_DIR := $(GET_LOCAL_DIR)
 MODULE := $(LOCAL_DIR)
 MODULE_CRATE_NAME := flagset
-MODULE_SRCS := \
-	$(LOCAL_DIR)/src/lib.rs \
-
+MODULE_RUST_CRATE_TYPES := rlib
+MODULE_SRCS := $(LOCAL_DIR)/src/lib.rs
 MODULE_RUST_EDITION := 2018
 MODULE_LIBRARY_DEPS := \
-	external/rust/crates/serde \
+
 
 include make/library.mk