buildtools: Restrict dynamic_lookup linker flag to macOS

Anoop C Srequested to merge
samba-team/devel/samba:anoopcs-fix-dynamic-lookup-ldflags into master

GNU ld.bfd interprets -Wl,-undefined,dynamic_lookup as a request for an undefined symbol named "dynamic_lookup", causing Linux i686 builds to fail. Only probe and add this macOS specific flag on macOS.

Checklist

  • Commits have Signed-off-by: with name/author being identical to the commit author
  • (optional) This MR is just one part towards a larger feature.
  • (optional, if backport required) Bugzilla bug filed and BUG: tag added
  • Test suite updated with functionality tests
  • Test suite updated with negative tests
  • Documentation updated
  • CI timeout is 3h or higher (see Settings/CICD/General pipelines/ Timeout)

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