Fix path mapping logic in `bootclasspath` for generated files

Copybara Import from https://github.com/bazelbuild/rules_java/pull/195

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Fix path mapping logic in `bootclasspath` for generated files (#195)

If the files comprising the Java runtime are not source files, the path to the Java home needs to be path mapped.

Work towards bazelbuild/bazel#22366

Closes #195
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COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_java/pull/195 from fmeum:java-home-path-map 43323b73d0f1bfc5ee24de64c2a9037746780879
PiperOrigin-RevId: 648662342
Change-Id: Idba93798982878d3f542b54d69c9536efd721db2