keystone: Add msm8937_32go target

For Android Go work, we add the android_target msm8937_32go.
Since there is no overlay for this target, we leave an empty
list for the overlap map.

Test: python development/keystone/container.py --android_target msm8937_32go; source build/envsetup; lunch msm8937_32go-userdebug; TEMPORARY_DISABLE_PATH_RESTRICTIONS=true make -j
Change-Id: Iac310bf65c2d83817543b4970d8e9256e3f3d8b4