Add ASAN prebuilt generation

Build a copy of the soong binaries with the address sanitizer enabled,
installed under prebuilts/build-tools/linux-x86/asan/{bin,lib*}. Only do
this for linux, since asan builds don't work on darwin.

Test: prebuilts/build-tools/build-prebuilts.sh
Change-Id: Ifdf878c74ffd03e83b2ac9723c4d205050bb38cb