RFR: 8339622: Regression in make open-hotspot-xcode-project

[Magnus Ihse Bursie]

Since [JDK-8338916](https://bugs.openjdk.org/browse/JDK-8338916), `make open-hotspot-xcode-project` fails with:


make[3]: *** No rule to make target `/Users/gerard/Work/bugs/8337563/jdk/build/macosx-aarch64-server-release/make-support/compile-commands/jvm-ldflags.txt', needed by `/Users/gerard/Work/bugs/8337563/jdk/build/macosx-aarch64-server-release/make-support/ide/xcode/_build_xcode_project_exec.marker'. Stop. 


The reason was that the ldflags file name changed in JDK-8338916, but this usage was not updated.

Also, when implementing this I had incorrectly used WORKSPACE_ROOT when I should have used TOPDIR.

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Commit messages:
 - 8339622: Regression in make open-hotspot-xcode-project

Changes: https://git.openjdk.org/jdk/pull/22571/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22571&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339622
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/22571.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22571/head:pull/22571

PR: https://git.openjdk.org/jdk/pull/22571