RFR: 8275145: file.encoding system property has an incorrect value on Windows

[Naoto Sato]

Fixing a regression in which `file.encoding` was initialized by `sprops->encoding` instead of `sprops->sun_jnu_encoding` on non macOS platforms. tier1-3 tests passed on all platforms.

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Commit messages:
 - 8275145: file.encoding system property has an incorrect value on Windows

Changes: https://git.openjdk.java.net/jdk/pull/5953/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5953&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275145
  Stats: 9 lines in 1 file changed: 8 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5953.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5953/head:pull/5953

PR: https://git.openjdk.java.net/jdk/pull/5953