RFR: 8368250: [AIX] now ubsan vptr check is also possible (follow up of JDK-8354686) [v2]

[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.

Joachim Kern has updated the pull request incrementally with one additional commit since the last revision:

  indentation and typo

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27468/files
  - new: https://git.openjdk.org/jdk/pull/27468/files/a459f293..e3f3a995

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27468&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27468&range=00-01

  Stats: 4 lines in 1 file changed: 0 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