[foreign-jextract] RFR: 8259226: jextract should differentiate between clang errors vs other runtime issues

[Athijegannathan Sundararajan]

CLANG_ERROR error code added. Also OUTPUT_ERROR exit code is used as expected.

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Commit messages:
 - 8259226: jextract should differentiate between clang errors vs other runtime issues

Changes: https://git.openjdk.java.net/panama-foreign/pull/429/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=429&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259226
  Stats: 176 lines in 22 files changed: 140 ins; 2 del; 34 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/429.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/429/head:pull/429

PR: https://git.openjdk.java.net/panama-foreign/pull/429