RFR: JDK-8334217 : [AIX] Misleading error messages after JDK-8320005

[Suchismith Roy]

dll_load_library() call fails is not analyzed (the ebuf content is ignored)
dll_load_library does not analyze the contents of ebuf which leads to misleading error message when library loading fails.

We now call  the second dll_load_library() only if the first returns with a 'No such file or directory' error message.
If the first dll_load_library() found the library is not able to load it by any reason, we do not try again with a .a extension.
[JDK-8334217](https://bugs.openjdk.org/browse/JDK-8334217)

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Commit messages:
 - check buffer
 - check ebuf

Changes: https://git.openjdk.org/jdk/pull/19887/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19887&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334217
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19887.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19887/head:pull/19887

PR: https://git.openjdk.org/jdk/pull/19887