RFR: 8252797: Non-PCH build fails on Ubuntu 16.4 when building with gtests

[Gerard Ziemski]

This is a workaround for GCC 5.4 bug that is triggered by a particular pattern of math header usage as is the case here with our gtest suite.

Thank you to Mikael Vidstedt for finding the GCC bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=14608 , triggered by gtest usage as described here https://github.com/google/googletest/commit/fe4d5f10840c5f62b984364a4d41719f1bc079a2

Thank you to Ioi for debugging the issue and coming up with the workaround used in this fix.

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

Commit messages:
 - workaround gcc math header bug

Changes: https://git.openjdk.java.net/jdk/pull/1678/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1678&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252797
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1678.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1678/head:pull/1678

PR: https://git.openjdk.java.net/jdk/pull/1678