feat: build and sign RPM packages

Passing files to Dom0 is always dangerous:

- Passing a git repository is dangerous as it can have ignored modified
  files and signature verification will pass.
- Passing an archive is troublesome for updates.
- Passing an RPM package depends on the RPM verification to be correct,
  some times it is not.
- Passing a RPM repository definition is less troublesome for the user,
  as it is a small file to verify the contents and update mechanism is
  via the package manager. Trust in RPM verification is still required.

Many improvements were made to the build scripts:

- requires-program: Single function to check if program is installed;
- spec-get: Sort project names for the usage message;
- spec-get: Only running commands that are necessary;
- spec-get: Fix empty summary when readme has copyright header;
- spec-gen: Fix grep warning of escaped symbol;
- spec-build: Sign RPM and verify signature;
- spec-build: Only lint the first SPEC for faster runtime;
- yumrepo-gen: Generate a local yum repository with signed metadata;
- qubesbuilder-gen: Generate a .qubesbuilder based on tracked projects;
- release: Build, sign and push all RPMs to repository.

Goal is to be able to build with qubes-builderv2 Qubes Executor.

For: https://github.com/ben-grande/qusal/issues/37

scripts/salt-lint.sh

@@ -39,8 +39,8 @@ if test -n "${1-}"; then
 fi
 
 case "${find_tool}" in
-  fd|fdfind) files="$(${find_tool} . minion.d/ --extension=conf) $(${find_tool} . salt/ --max-depth=2 --type=f --extension=sls --extension=top)";;
-  find) files="$(find minion.d/ -type f -name "*.conf") $(find salt/* -maxdepth 2 -type f \( -name '*.sls' -o -name '*.top' \))";;
+  fd|fdfind) files="$(${find_tool} . minion.d/ --extension=conf) $(${find_tool} . salt/ --max-depth=2 --type=f --extension=sls --extension=top | sort -d)";;
+  find) files="$(find minion.d/ -type f -name "*.conf") $(find salt/* -maxdepth 2 -type f \( -name '*.sls' -o -name '*.top' \) | sort -d)";;
 esac
 
 exec salt-lint ${conf} ${files}