RFR: 8310376: Extend SetupTarget macro with DIR parameter

[Erik Joelsson]

To allow for more flexibility when using the SetupTarget macro in a custom extension of Main.gmk, I would like to add a DIR parameter, which is the directory the sub make command CDs into before calling make. It defaults to $(TOPDIR)/make. This parameter should be set when the target makefile of the call is located in a different directory.

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Commit messages:
 - JDK-8310376

Changes: https://git.openjdk.org/jdk/pull/14560/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14560&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310376
  Stats: 7 lines in 1 file changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14560.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14560/head:pull/14560

PR: https://git.openjdk.org/jdk/pull/14560