[foreign-jextract] RFR: 8268160: jextract tool provider should avoid security manager usage

[Athijegannathan Sundararajan]

jextract is not incubated in JDK as of now. By the time it makes into JDK (if it does), security 
manager would have been removed. Removing security manager usage in jextract code.

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Commit messages:
 - 8268160: jextract tool provider should avoid security manager usage

Changes: https://git.openjdk.java.net/panama-foreign/pull/546/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=546&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268160
  Stats: 9 lines in 1 file changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/546.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/546/head:pull/546

PR: https://git.openjdk.java.net/panama-foreign/pull/546