RFR: 8284732: FFI_GO_CLOSURES macro not defined but required for zero build on Mac OS X

[Johannes Bechberger]

It just codifies the current behavior as it defines `FFI_GO_CLOSURES` to be `0`.

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Commit messages:
 - 8284732: FFI_GO_CLOSURES macro not defined but required for zero build on Mac OS X

Changes: https://git.openjdk.java.net/jdk/pull/8195/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8195&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284732
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8195.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8195/head:pull/8195

PR: https://git.openjdk.java.net/jdk/pull/8195