RFR: JDK-8276572: Fake libsyslookup.so library causes tooling issues

[Andrew John Hughes]

The lack of anything to compile in `syslookup.c` is leading to a number of issues in our tooling, on some architectures more than others (s390x seems to be the most problematic).  They expect to be able to retrieve debuginfo and compiler flags from generated .so files and fail with libsyslookup.so

This simple patch adds a dummy function to `syslookup.c` so it appears more like a regular file to be compiled. I can't see this causing a problem with the symbol lookup, but we could filter it out on the Java side if need be.

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Commit messages:
 - JDK-8276572: Fake libsyslookup.so library causes tooling issues

Changes: https://git.openjdk.java.net/jdk/pull/6245/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6245&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276572
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6245.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6245/head:pull/6245

PR: https://git.openjdk.java.net/jdk/pull/6245