Fixes for compiling crypto in older trees

Some of these fixes needed to be made anyway. Note that older
trees will still need to have files / repos copied into them from
newer trees. Namely we need:
system/security/softkeymaster
hardware/libhardware/include/hardware/keymaster.h

Maybe others as I did not document very carefully what I was
pulling in.

Change-Id: I465fd1fbe228803ec02fba047b151f07ea13d5ca
diff --git a/crypto/scrypt/tests/Android.mk b/crypto/scrypt/tests/Android.mk
index 07c2102..c20b41d 100644
--- a/crypto/scrypt/tests/Android.mk
+++ b/crypto/scrypt/tests/Android.mk
@@ -20,6 +20,7 @@
     libgtest \
     libgtest_main
 
+LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE := scrypttwrp_test
 
 include $(BUILD_NATIVE_TEST)