scripts/oss-fuzz: give all fuzzers -target names

scripts/oss-fuzz: give all fuzzers -target names

We switched to hardlinks in
a942f64cc4 ("scripts/oss-fuzz: use hardlinks instead of copying")

The motivation was to conserve space (50 fuzzers built with ASAN, can
weigh close to 9 GB).

Unfortunately, OSS-Fuzz (partially) treated the underlying copy of the
fuzzer as a standalone fuzzer. To attempt to fix, we tried:

f8b8f37463 ("scripts/oss-fuzz: rename bin/qemu-fuzz-i386")

This was also not a complete fix, because though OSS-Fuzz
ignores the renamed fuzzer, the underlying ClusterFuzz, doesn't:
https://storage.googleapis.com/clusterfuzz-builds/qemu/targets.list.address
https://oss-fuzz-build-logs.storage.googleapis.com/log-9bfb55f9-1c20-4aa6-a49c-ede12864eeb2.txt
(clusterfuzz still lists qemu-fuzz-i386.base as a fuzzer)

This change keeps the hard-links, but makes them all point to a file
with a qemu-fuzz-i386-target-.. name. If we have targets, A, B, C, the
result will be:

qemu-fuzz-i386-target-A (base file)
qemu-fuzz-i386-target-B -> qemu-fuzz-i386-target-A
qemu-fuzz-i386-target-C -> qemu-fuzz-i386-target-A

The result should be that every file that looks like a fuzzer to
OSS-Fuzz/ClusterFuzz, can run as a fuzzer (we don't have a separate base
copy). Unfortunately, there is not simple way to test this locally.

In the future, it might be worth it to link the majority of QEMU in as a
shared-object (see https://github.com/google/oss-fuzz/issues/4575 )

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20201108171136.160607-1-alxndr@bu.edu>
Signed-off-by: Thomas Huth <thuth@redhat.com>