RFR: JDK-8313244: NM flags handling in configure process [v2]

[Andreas Steiner]

> On AIX we need the -X64 option for NM in the build. The handling is equivalent to the other used tools flags like AR.
> This change will replace the quick fix done in https://bugs.openjdk.org/browse/JDK-8312466.

Andreas Steiner has updated the pull request incrementally with one additional commit since the last revision:

  remove needless else

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15150/files
  - new: https://git.openjdk.org/jdk/pull/15150/files/acc1b79f..6752fc12

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15150&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15150&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15150.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15150/head:pull/15150

PR: https://git.openjdk.org/jdk/pull/15150