RFR: 8338675: javac shouldn't silently change .jar files on the classpath [v8]

[David Beaumont]

> Modifying `JavacFileManager` to skip creating sibling output class files for source files found in JARs.
> 
> This should match older (JDK 8) behavior whereby the JAR was not writable, and results in any newly generated class files being written to the current working directory (the output of class files into current directory isn't good, but it should match the old behavior).

David Beaumont has updated the pull request incrementally with one additional commit since the last revision:

  Add final test for sourcepath entry (same behaviour).

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23699/files
  - new: https://git.openjdk.org/jdk/pull/23699/files/1341c7c7..6fcea57f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23699&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23699&range=06-07

  Stats: 21 lines in 1 file changed: 19 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23699.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23699/head:pull/23699

PR: https://git.openjdk.org/jdk/pull/23699