Create dexpreopt.config in build_linux_bionic.sh

soong will panic if a json file called $PRODUCT_OUT/dexpreopt.config
is not present. This file normally contains information from make
soong needs to implement half of the dexpreopt support. Since this
support still requires some make parts it is not needed for
linux_bionic builds.

Test: ./art/tools/build_linux_bionic.sh -j72 com.android.runtime.host
Bug: 120436895
Change-Id: Id63e39eefbf5217de05738691f52c352cb1529ee