[jfx11u] RFR: 8268915: WebKit build fails with Xcode 12.5

[Kevin Rushforth]

Clean backport of fix to rename `VERSION` to `VERSION.txt` to fix build breakage on Xcode 12.5.

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Commit messages:
 - 8268915: WebKit build fails with Xcode 12.5

Changes: https://git.openjdk.java.net/jfx11u/pull/31/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=31&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268915
  Stats: 0 lines in 1 file changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/31.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/31/head:pull/31

PR: https://git.openjdk.java.net/jfx11u/pull/31