Refactor RPM variables/arguments
This MR simplifies some pipeline branching:
- Renames
RPMBUILD_ARGS
toRPMBUILD_ARCH_ARGS
to make it clear that they are architecture-specific - Renames
RPMBUILD_EXTRA_ARGS
toRPMBUILD_ARGS
- Creates the
BUILD_KABI_WHITELIST
variable to determine when the noarch kabi whitelist RPM must be built - Adds
RPMBUILD_TREE_ARGS
to allow tree YAML to inject additional variables depending on the tree under test