Fix Mynewt builds; add log stub dependency

A recent change in the Mynewt repo
(b10cbea5ef882e7f91d1c34ffcf2506d3e183003) imposes the LOG API
requirement on the `sys/mfg` package.  To fix broken builds, make the
Mynewt app and test package depend on `sys/log/stub`.

Signed-off-by: Christopher Collins <ccollins@apache.org>
diff --git a/boot/mynewt/pkg.yml b/boot/mynewt/pkg.yml
index 1cbd1ab..d2c6eed 100644
--- a/boot/mynewt/pkg.yml
+++ b/boot/mynewt/pkg.yml
@@ -33,6 +33,7 @@
     - "@mcuboot/boot/bootutil"
     - "@mcuboot/boot/mynewt/flash_map_backend"
     - "@apache-mynewt-core/kernel/os"
+    - "@apache-mynewt-core/sys/log/stub"
 
 pkg.deps.BOOTUTIL_NO_LOGGING:
     - "@apache-mynewt-core/sys/console/stub"