Add -Werror.

Also, fixed several warnings (including one bug in generateCppImpl.cpp).

Test: compiles

Bug: 32559427

Change-Id: I78375b9052c0ad447ebac638258f25bbf562712f
diff --git a/c2hal/Android.bp b/c2hal/Android.bp
index a634ed6..03987f5 100644
--- a/c2hal/Android.bp
+++ b/c2hal/Android.bp
@@ -16,9 +16,9 @@
     "test",
 ]
 
-
 cc_binary_host {
     name: "c2hal",
+    cflags: hidl_flags,
     srcs: [
         "AST.cpp",
         "c2hal_l.ll",
@@ -43,10 +43,5 @@
         "libhidl-gen-utils",
     ],
 
-    static_libs: ["libutils"],
-
-    cflags: [
-        "-O0",
-        "-g",
-    ],
+    static_libs: ["libutils"]
 }