arm-trusted-firmware: set unfreeIncludeHDCPBlob=false if not used

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This is an alternative to #174691; please do not merge both, just one or the other.

Compared to #174691 this PR breaks out buildArmTrustedFirmware into a separate file build.nix so it has its own 'callPackageinvocation, separate from the CPU-specific expressions which were previously in the same file. This allows to eliminate the redundantunfreeIncludeHDCPBlob` parameter.

Now each expression has exactly one parameter in scope:

• buildArmTrustedFirmware has a parameter deleteHDCPBlobBeforeBuild

• armTrustedFirmware${PLATFOM} has a parameter unfreeIncludeHDCPBlob

Description of changes

The unfreeIncludeHDCPBlob parameter was introduced as a result of this reviewer request:

#148890 (comment)

The default value unfreeIncludeHDCPBlob?true causes a change in the meta.license field for all of the subpackages within pkgs/misc/arm-trusted-firmware/, and results in them needing NIXPKGS_ALLOW_NONFREE=1.

For Rockchip platforms this change is unavoidable; we are correcting an incorrect license declaration. However for non-Rockchip platforms the file hdcp.bin does not get included in the output. Therefore we can set unfreeIncludeHDCPBlob=false on these platforms and produce no user-visible change in the resulting output, while preserving the ability to build them without NIXPKGS_ALLOW_NONFREE=1.

Let's do that.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

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Closed by #174691