Revert "cgo: set cgo compiler flags in backend.go"

This reverts commit 09416b1d.

required pkg-config .pc files are not provided by the qt project on linux the distribution packages contains them but on windows and macOS these are not available causing build to fail

ref: https://bugreports.qt.io/browse/QTBUG-86080

added 5 commits

• 6dd96187...0236703b - 4 commits from branch leap:main
• 7a625b02 - Revert "cgo: set cgo compiler flags in backend.go"

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enabled an automatic merge when the pipeline for 7a625b02 succeeds

aborted the automatic merge because target branch was updated

added 6 commits

• 7a625b02...b9fc3584 - 5 commits from branch leap:main
• 214a482e - Revert "cgo: set cgo compiler flags in backend.go"

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merged