RFR: 8366836: Don't execute post-IncludeCustomExtension if file was not included

[Erik Joelsson]

On Wed, 3 Sep 2025 18:49:51 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> There is a bug in make/common/MakeIncludeEnd.gmk, which makes it always include the "post" custom extension. In MakeIncludeStart.gmk, the "pre" custom extension is properly guarded by the check if the file has not already been included. This is not the case for the "post" condition, so a custom "post" hook can be included multiple times.

Marked as reviewed by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27077#pullrequestreview-3182335380