[jdk17u] RFR: 8274293: Build failure on macOS with Xcode 13.0 as vfork is deprecated

[xpbob]

Backport 252aaa9249d8979366b37d59487b5b039d923e35

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Commit messages:
 - Backport 252aaa9249d8979366b37d59487b5b039d923e35

Changes: https://git.openjdk.java.net/jdk17u/pull/183/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=183&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274293
  Stats: 10 lines in 2 files changed: 8 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/183.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/183/head:pull/183

PR: https://git.openjdk.java.net/jdk17u/pull/183