Use -Werror in external/lmfit

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I081939a4a6512c43683e7b4e88307ebf6ea2721e
diff --git a/Android.bp b/Android.bp
index 2bc9a21..099216e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -21,6 +21,11 @@
         "lib/lmcurve_tyd.c",
         "lib/lmmin.c",
     ],
-    cflags: ["-W", "-Wall", "-Wno-unused-parameter"],
+    cflags: [
+        "-W",
+        "-Wall",
+        "-Werror",
+        "-Wno-unused-parameter",
+    ],
     export_include_dirs: ["lib"],
 }