These are now processed in afl-qemu-trace so that the "copy+paste" code
that is in all of the other AFL tools can be removed.
This also allows the AFL_USE_QASAN flag to work the same when used
with tools like afl-fuzz as it does with afl-qemu-trace. This is
important in situations where loading the QASAN library changes
the address of your desired entrypoint, or for crash validation
using the same environment that afl-fuzz was using.
With this change, the same set of environment variables can be used
in exactly the same way between afl-fuzz, afl-showmap, and
afl-qemu-trace, and you will get exactly the same guest environment.
In QEMU mode (-Q), setting AFL_QEMU_CUSTOM_BIN cause afl-fuzz to skip
prepending afl-qemu-trace to your command line. Use this if you wish to use a
custom afl-qemu-trace or if you need to modify the afl-qemu-trace arguments.
Add checks to free() and malloc_usable_size() to
verify (sort of) that the pointers are actually
pointing at valid allocated memory before dereferencing
them and using the chunk_begin struct info.
This will catch use-after-free and wildly bad pointers
a little bit earlier.
Most of these packages (bison, flex, pixman (in non-system mode)) are no
longer dependencies of QEMU and regardless, QEMU's build system is quite
capable of finding dependencies by itself and will error out
accordingly. This prevents having to further change this code as QEMU's
dependencies inevitably change.
