Add a CMAKE option to completely disable Python

[lbartoletti]

Description

I'm opening this PR to discuss whether we should introduce an additional layer of restriction when disabling Python in QGIS. Is the WITH_BINDINGS flag sufficient to completely disable Python or should be enforced?

While WITH_BINDINGS disables PyQGIS support, if the goal is to entirely remove Python—especially for security reasons—is that enough? For example, I'm thinking about the pyplugin-installer, which is used with QGIS_DESTKTOP. Moreover, the CMakeLists file adds dependencies for pycore, pygui, and pyanalysis, yet I can't seem to locate them.

Is it necessary to include the src/python directory when WITH_BINDINGS is set to false?

Any thoughts?

[github-actions]

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[nyalldawson]

I'm opening this PR to discuss whether we should introduce an additional layer of restriction when disabling Python in QGIS. Is the WITH_BINDINGS flag sufficient to completely disable Python or should be enforced?

I'm personally +1 to an opt-in "qgis with no python", I can definitely understand the rationale behind this. (The biggest impact of this is that the build will have NO processing support 🙀 )

[rouault]

The new option should be mentioned at https://github.com/qgis/QGIS/blob/master/INSTALL.md#371-available-compilation-flags

[nyalldawson]

@lbartoletti i think you force-pushed and dropped the fixes from my earlier comments