Move error_code.h into otautil.

This way it stops requiring relative path ".." in LOCAL_C_INCLUDES
(uncrypt and edify). Soong doesn't accept non-local ".." in
"local_include_dirs".

Test: mmma bootable/recovery
Change-Id: Ia4649789cef2aaeb2785483660e9ea5a8b389c62
diff --git a/otautil/Android.bp b/otautil/Android.bp
index 9cde7ba..5905ba6 100644
--- a/otautil/Android.bp
+++ b/otautil/Android.bp
@@ -15,6 +15,8 @@
 cc_library_static {
     name: "libotautil",
 
+    host_supported: true,
+
     srcs: [
         "SysUtil.cpp",
         "DirUtil.cpp",