pvmfw: suppress error about unused -c argument

Change-Id: I86b9c97381b2022c96b34469687be40d89198342
diff --git a/guest/pvmfw/Android.bp b/guest/pvmfw/Android.bp
index 51f7802..793204d 100644
--- a/guest/pvmfw/Android.bp
+++ b/guest/pvmfw/Android.bp
@@ -384,6 +384,8 @@
         "-E",
         "-P",
         "-xassembler-with-cpp", // allow C preprocessor directives
+        // Suppress an error about the unused -c that precedes -S.
+        "-Wno-unused-command-line-argument",
     ],
     visibility: ["//visibility:private"],
 }