Build - Allow individual projects to enforce a property's value

Some projects require system properties to be set to a specific
value (for example, a shared library needing a property pointing
to its own path) in order to work correctly, but some device
configurations are mistakenly setting those properties with the
wrong value (usually inherited from the original OEM build).

"PRODUCT_PROPERTY_UBER_OVERRIDES += property=value" can (and
should) be used in that project's makefile to ensure the value
is the correct one. This variable is intended for software projects,
and should never be used in product makefiles (BoardConfig, cm.mk,
AndroidProduct)

Change-Id: Ia0ccac81bd4cbaee65c9c58efe7cdbca5bc11c5a
Signed-off-by: STELIX <ssspinni@gmail.com>
Build - Store the value from TARGET_OTA_ASSERT_DEVICE to a file

This is needed so it can be read in when re-signing a package to
allow for the proper device asserts.

Change-Id: Icc9502e1456ca51717df5797d785f548b76c3d53
Signed-off-by: STELIX <ssspinni@gmail.com>