RFR: 8282239 [testbug, AIX] ProcessBuilder/Basic.java fails with incorrect LIBPATH [v2]

[Tyler Steele]

> This test had two failing sections on AIX related to an incorrect expected value for LIBPATH. The two (previously failing) test sections are below. 
> 
> - Test Runtime.exec(...envp...) with envstrings with initial `='
> - Test Runtime.exec(...envp...) with envstrings containing NULs
> 
> This PR modifies the environment passed to the process at ...exec(cmdp, **envp**) to include the LIBPATH of the parent. With this change, the expected libpath matches the libpath returned by the process.
> 
> ### Alternatives
> 
> An equivalent change would be to modify the libpath variable used to set the expected value for the test without explicitly setting the LIBPATH in process invocation. This would involve removing the libpath for .../jtreg/native that is added by the test runner by command-line option `-J-Dtest.nativepath=...images/test/jdk/jtreg/native `. This change would be reasonable, but I prefer the approach taken in this PR.
> 
> ### Testing
> 
> This test now passes on my test machine running AIX 7.1.

Tyler Steele has updated the pull request incrementally with one additional commit since the last revision:

  Updates copyright year & adds bugid

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7581/files
  - new: https://git.openjdk.java.net/jdk/pull/7581/files/5d325951..fd3a84ed

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7581&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7581&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7581.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7581/head:pull/7581

PR: https://git.openjdk.java.net/jdk/pull/7581