RFR: JDK-8283562: JDK-8282306 breaks gtests on zero

[Thomas Stuefe]

Trivial workaround for zero.

[JDK-8282306](https://bugs.openjdk.java.net/browse/JDK-8282306) introduced os.is_first_C_frame_vm gtest, but that breaks on zero since the test relies on os::current_frame(), which on all zero platforms is almost empty.

As a workaround, I disable the test. A potential solution would be to use getcontext(3) in `os::current_frame()`, but lets just exclude the test for now.

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Commit messages:
 - JDK-8283562-JDK-8282306-breaks-gtests-on-zero

Changes: https://git.openjdk.java.net/jdk/pull/7920/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7920&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283562
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7920.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7920/head:pull/7920

PR: https://git.openjdk.java.net/jdk/pull/7920