The first hunk of the riscv64 patch adds an else-if branch to
this_arch_root() in
crates/lib/src/discoverable_partition_specification.rs. Upstream bootc
accepted the same change in commit 47c3620 ("fix: add riscv64 to
this_arch_root"), shipped in v1.15.2. As a result the hunk now matches
already-applied code and `patch -f --fuzz=0` fails the whole %prep,
breaking build #56177 on every arch.
Drop that hunk; keep the two install.rs / install/baseline.rs hunks,
which upstream still does not have.
