Disabled modules shouldn't call pkg-config if they are set to be non-builtin

[Calinou]

Godot version: Git 72d87cf

OS/device including version: Fedora 30

Issue description: Someone reported on IRC that non-builtin dependency checking is done even if the module that requires them is disabled. This causes a build failure if the dependency in question isn't installed on the system.

For instance, builtin_libtheora=no will always call pkg-config, even if module_theora_enabled=no is also passed to the SCons command line:

godot/platform/x11/detect.py

Lines 241 to 247 in 72d87cf

	# Sound and video libraries
	# Keep the order as it triggers chained dependencies (ogg needed by others, etc.)
	if not env['builtin_libtheora']:
	env['builtin_libogg'] = False # Needed to link against system libtheora
	env['builtin_libvorbis'] = False # Needed to link against system libtheora
	env.ParseConfig('pkg-config theora theoradec --cflags --libs')

Steps to reproduce: Build Godot with scons platform=x11 builtin_libtheora=no module_theora_enabled=no.

[akien-mga]

builtin_*=no should only be used if you want to link against the system provided version. If you don't want to use theora, the module_theora_enabled=no flag should be used.

This could be made more robust but would require substantial changes, and a proper dependency checking system à la configure.

[Calinou]

@akien-mga What about replacing if not env['builtin_libtheora']: with if env['module_theora_enabled'] and not env['builtin_libtheora']: (and doing the same for other modules with non-builtin dependency options)?

[KoBeWi]

Can anyone still reproduce this bug in Godot 3.2.3 rc6 or any later release?

[akien-mga]

It's likely still valid yes.