RFR: 8307110: zero build broken after JDK-8304265

[Jorn Vernee]

These changes were accidentally omitted from https://github.com/openjdk/jdk/pull/13079

When building the zero VM on aarch64 and linux-x86 in our CI, compilation of `libFallbackLinker.c` fails because the function `ffi_get_struct_offsets` can not be found.

The issue is that the libffi version found on some of our build systems is too old, and doesn't contain the required function. This patch switches away from using the libffi found on the system, and to using a pre-built libffi 3.4.2 package (as we already do for linux-x64-zero)

I tried getting the linux-x86-zero build working as well, but it's broken for other reasons. I've at least verified that it compiles `libFallbackLinker.c` when using libffi 3.4.2

Testing: building linux-aarrch64-zero & linux-aarrch64-zero-debug, as well as linux-x86-zero and linux-x86-zero-debug (the x86 builds failed for other reasons)

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Commit messages:
 - use libffi artifact for other zero build configurations

Changes: https://git.openjdk.org/jdk/pull/13728/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13728&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307110
  Stats: 7 lines in 2 files changed: 4 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13728.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13728/head:pull/13728

PR: https://git.openjdk.org/jdk/pull/13728