RFR: Add support for bin folder in makefile [v2]

[Maurizio Cimadamore]

> A previous PR changed the gradle build to emit launcher scripts in a separate "bin" folder. However, that PR did not make any changes to the makefiles used to produce the binary bundles. This PR rectifies that.
> 
> Tested locally.

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Set correct permissions for linux script, to mimic what gradle does

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Changes:
  - all: https://git.openjdk.org/jextract/pull/247/files
  - new: https://git.openjdk.org/jextract/pull/247/files/8c98876d..620fbd7b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=247&range=01
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=247&range=00-01

  Stats: 2 lines in 2 files changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jextract/pull/247.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/247/head:pull/247

PR: https://git.openjdk.org/jextract/pull/247