RFR: 8368250: [AIX] now ubsan vptr check is also possible (follow up of JDK-8354686)

[Joachim Kern]

After [JDK-8354686](https://bugs.openjdk.org/browse/JDK-8354686) the ubsan vptr checks still did not work. We finally found out, that they only work, if all linkage units are linked with the C++ compiler frontend as linker, especially the main executables (java, javac, ...) which are linked with the C compiler frontend.
So for a ubsan enabled build on AIX we let everything link with the C++ compiler frontend.
Background: The C++ compiler frontend inherently adds special static libraries which the C compiler does not. This results in missing symbols when trying to start a program and its shared libraries, when they were linked in mixed mode.

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

Commit messages:
 - JDK-8368250

Changes: https://git.openjdk.org/jdk/pull/27468/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27468&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368250
  Stats: 9 lines in 3 files changed: 5 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/27468.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27468/head:pull/27468

PR: https://git.openjdk.org/jdk/pull/27468