RFR: 8286940: [IR Framework] Allow IR tests to build and use Whitebox without -DSkipWhiteBoxInstall=true [v2]

[Christian Hagedorn]

> Currently, the IR framework always tries to install the Whitebox by moving the Whitebox class file to the JTreg class path. However, when a test already builds the Whitebox and uses it as part of the test, we cannot access it on certain platforms. On Windows, for example, we'll get the following exception:
> 
> Caused by: java.nio.file.FileSystemException: sun\hotspot\WhiteBox.class: The process cannot access the file because it is being used by another process
> 
> To mitigate this problem, one can specify `-DSkipWhiteBoxInstall=true` which was already done in [JDK-8283187](https://bugs.openjdk.java.net/browse/JDK-8283187). But this is not a good solution as the user should not need to worry about the inner workings of the IR framework.
> 
> I propose to get rid of this flag by reworking the Whitebox installation process.
> 
> Thanks,
> Christian

Christian Hagedorn has updated the pull request incrementally with one additional commit since the last revision:

  Update test/hotspot/jtreg/compiler/lib/ir_framework/TestFramework.java
  
  Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8879/files
  - new: https://git.openjdk.java.net/jdk/pull/8879/files/0b0b7d37..8f2a7c70

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8879&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8879&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8879.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8879/head:pull/8879

PR: https://git.openjdk.java.net/jdk/pull/8879