Set ArtTargetIncludeDebugBuild only with true

ArtTargetIncludeDebugBuild is being set as true when
PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD is false, because add_json_bool
is not using value of the string, and just set as true if non-empty
instead.

Bug: 403309968
Test: ArtTargetIncludeDebugBuild is false when
PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD is false

Change-Id: I3e7db2f3073067ff02d6a5d12ae3966e721bb304