[jdk11u-dev] RFR: 8211438: [Testbug] runtime/XCheckJniJsig/XCheckJSig.java looks for libjsig in wrong location

[Amos Shi]

Backport of [JDK-8211438](https://bugs.openjdk.org/browse/JDK-8211438)
Note. 
- `test/hotspot/jtreg/ProblemList.txt` No need to change because the line has been removed already
- `src/java.base/unix/native/libjsig/jsig.c` Add include section to fix compile error; the include was originally added by [JDK-8200609](https://bugs.openjdk.org/browse/JDK-8200609)

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

Commit messages:
 - Backport d872314ef3f9a9c3fdea88d097867599c8e08494

Changes: https://git.openjdk.org/jdk11u-dev/pull/2319/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2319&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8211438
  Stats: 26 lines in 2 files changed: 12 ins; 8 del; 6 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2319.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2319/head:pull/2319

PR: https://git.openjdk.org/jdk11u-dev/pull/2319