RFR: 8274293: Build failure with Xcode 13.0 due to vfork is deprecated [v2]

[xpbob]

> remove vfork() on Darwin

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

  Drop drop "Solaris" from the comment

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5686/files
  - new: https://git.openjdk.java.net/jdk/pull/5686/files/89bb9c31..27d19543

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5686&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5686&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5686.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5686/head:pull/5686

PR: https://git.openjdk.java.net/jdk/pull/5686