Configure backend for module THEOS_PACKAGE_SCHEMEs and modularize rootless scheme

[L1ghtmann]

What does this implement/fix? Explain your changes.

• Adds $THEOS_MODULE_PATH/schemes/
• Adds said directory to the module include statement
• Abstracts out rootless scheme logic to its own module
• Ignores said module in gitignore
• exports THEOS_PACKAGE_INSTALL_PREFIX in package.mk
• includes module version of package.mk in package.mk prior to including the normal and module versions of the package-format.mk
• Includes portable stage changes (Use additional temporary stage for package schemes  #775)
• Includes rootless install_name changes (Handle @rpaths for libs/frameworks when building for rootless #737)

Does this close any currently open issues?

No

Any relevant logs, error output, etc?

Any other comments?

• Tested package structures and load/id cmds briefly with dpkg-deb/otool, respectively
  • Please double check these
• Supersedes the two prs mentioned above
• Would benefit from Minor rootless impl adjustments #712, Respect package scheme when installing frameworks #744, and Mimic frameworks by installing libraries to THEOS_LIBRARY_PATH in internal stage #748
• Enables other schemes, such as RootHide, to be added as easily as, say, theos-jailed without needing to pr/switch branches
• Totally open to changes, did this real quick since I had a bit

Where has this been tested?

Operating System: …

Linux (WSL)

Platform: …

Target Platform: …

Toolchain Version: …

SDK Version: …

[kabiroberai]

Love the idea of adding schemes via modules — hope to give this a more thorough review when I have the chance but no blockers atm

[kabiroberai]

I wonder whether we should deprecate explicitly setting THEOS_PACKAGE_SCHEME in favour of MODULES = <scheme>

[L1ghtmann]

I debated that as well. My current thought process is that schemes are modules, but modules aren't necessarily schemes, so keeping the associated variables separate continues that trend. Also helps make managing the necessary changes to internal Theos processes (e.g., stage) easier as we know the state of THEOS_PACKAGE_SCHEME is either a valid scheme or blank.

[L1ghtmann]

Actually, now that I think about it, the stage changes I propose rely on THEOS_PACKAGE_INSTALL_PREFIX, not THEOS_PACKAGE_SCHEME. The only instance where we seem to rely on THEOS_PACKAGE_SCHEME internally is when we modify the linker's library search paths.

[leptos-null]

Looks great to me.

Testing:

(for which I created a module called leptos_mod and placed in $THEOS/mod)

• make package
• make THEOS_PACKAGE_SCHEME=rootless package
• make MODULES=leptos_mod package
• make THEOS_PACKAGE_SCHEME=rootless MODULES=leptos_mod package
• make "MODULES = leptos_mod rootless" package

Inspected tree of .theos/_ and used otool to verify build products.