RFR: 7903191: Fix build with "MAKEFLAGS=-j32". [v2]

[Jan Kratochvil]

> A parallel build needlessly errors out:

Jan Kratochvil 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:

  Fix build with "MAKEFLAGS=-j32".
  
  /bin/sh: line 5: jtreg/build/classes/com/sun/javatest/regtest/tool/jars.properties: No such file or directory
  make: *** [jtreg.gmk:98: jtreg/build/classes/com/sun/javatest/regtest/tool/jars.properties] Error 1

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Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/72/files
  - new: https://git.openjdk.java.net/jtreg/pull/72/files/18b1d4fc..7e04c214

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=72&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=72&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/72.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/72/head:pull/72

PR: https://git.openjdk.java.net/jtreg/pull/72