RFR: 8308407: libjvm library not reproducibly comparable between vendors [v4]

[Andrew Leonard]

> This PR fixes issue: https://bugs.openjdk.org/browse/JDK-8308407
> 
> It ensures that the C compilation of abstract_vm_version.o generates a minimum 64byte static C const for vm_vendor, thus ensuring for most Vendor builds the object has a 64byte string char array.
> 
> Since this is just a nul terminated string as before, just within a fixed 64byte location, and should a longer Vendor string be specified it will be longer, there is no change in behavior. It purely provides a fixed 64byte string array in the compiled object, which for most if not all Vendors will be sufficient.

Andrew Leonard has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' of github.com:openjdk/jdk into vendorpad
   Merge latest upstream changes.
 - 8308407: libjvm library not reproducibly comparable between vendors
   
   Signed-off-by: Andrew Leonard <anleonar at redhat.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14058/files
  - new: https://git.openjdk.org/jdk/pull/14058/files/bba47c30..9ef8ebcb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14058&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14058&range=02-03

  Stats: 10830 lines in 422 files changed: 4948 ins; 4493 del; 1389 mod
  Patch: https://git.openjdk.org/jdk/pull/14058.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14058/head:pull/14058

PR: https://git.openjdk.org/jdk/pull/14058