RFR: 8296872: gtest is built with the build-jdk

[Magnus Ihse Bursie]

The build-jdk is a JDK built on the current sources that can execute on the build platform. This is needed when cross-compiling, in addition to the boot-jdk (which runs on the build platform, but is an older version of the JDK), and is different from the JDK resulting from the build (which can only execute on the target platform).

If we do not supply a pre-built build-jdk, the build system creates a new, on the fly, before starting the compilation proper. 

This build-jdk includes gtest for hotspot, if available. This is just a waste of resources (and actually triggered a bug; which is how it was discovered).

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Commit messages:
 - 8296872: gtest is built with the build-jdk

Changes: https://git.openjdk.org/jdk/pull/11106/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11106&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296872
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/11106.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11106/head:pull/11106

PR: https://git.openjdk.org/jdk/pull/11106