[jdk8u-dev] RFR: 8286989: Build failure on macOS after 8281814

[zzambers]

This fixes wrong paths to debuginfo files passed to zip command, causing build failure on MacOS in github workflow. Problem was introduced by JDK-8281814 [1] (integrated, while github workflow PR was still in progress). 

I have done some experiments [2] and found out, that on macos, debuginfo files are stored in additional directories, relative to directory where object files are stored. Removing all directory components is therefore not correct on macos. Two seemingly equivalent fixes were were considered in JDK-8281814 (using notdir and using subst), but chosen one was not the correct one.

Follows example which illustrates difference of different variants of said zip command:

**Prior to JDK-8281814:**
$(ZIP) -q $$@ $$($1_DEBUGINFO_FILES)
- macos:

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Commit messages:
 - Fixed debuginfo files paths on MacOS

Changes: https://git.openjdk.java.net/jdk8u-dev/pull/61/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=61&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286989
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk8u-dev/pull/61.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-dev pull/61/head:pull/61

PR: https://git.openjdk.java.net/jdk8u-dev/pull/61