RFR: 8273774: CDSPluginTest should only expect classes_nocoops.jsa exists on supported 64-bit platforms [v3]

[Remilia Scarlet]

> Currently, the Platform.is64Bit() hard coded for judging whether the target arch is 64-bit.
> The `classes_nocoops.jsa not found` issue can be found while testing CDSPluginTest.java on 64-bit platform, excluding x64 and AARCH64, like mips64.
> 
> For solving this issue, we assume that the bits of target UNKNOWN arch is same as the runtime platform.
> This patch adds the following lines in the Platform.is64Bit() method.
> 
> ``` java
> if (arch() == Platform.Architecture.UNKNOWN) {
>      return (System.getProperty("os.arch").indexOf("64") != -1);
> }
> 
> 
> Please review this change. Thanks!

Remilia Scarlet has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8273774: CDSPluginTest should only expect classes_nocoops.jsa exists on supported 64-bit platforms

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5519/files
  - new: https://git.openjdk.java.net/jdk/pull/5519/files/125c83e7..5ec04d45

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5519&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5519&range=01-02

  Stats: 12 lines in 2 files changed: 6 ins; 4 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5519.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5519/head:pull/5519

PR: https://git.openjdk.java.net/jdk/pull/5519