Resolves item #3 of docs/working/archive/session-logs/2026-07-24-punch-list.md
("riscv64 hosted build isn't reachable via plain make"), the last open
item from that list. Decided against options (b) chasing GCC's riscv64
nanosleep-visibility failure at its root (undiagnosed, open-ended) and
(c) leaving it manual — instead wired the already-verified clang recipe
(commit 4485c38 / e287334) into the Makefile, mirroring the existing
rpi4-cross pattern.
Makefile: new riscv64-clang target. CFLAGS deliberately does not reuse
$(BASE_CFLAGS) (hardcodes -std=c99); clang needs -std=c11 -pthread here
instead. Registered in `make help` and .PHONY.
docs/lithosananke/hosted-acceptance-test/README.md: riscv64 section now
points at `make riscv64-clang` instead of the long manual invocation.
Updated Background section and commit list to reflect that all three
punch-list items touching this doc (#1 asm fix, #2 doc command, #3 make
target) are now resolved.
Verified: `make riscv64-clang` produces a binary with identical results
to the manual command it replaces (965 passed / 0 failed, "ALL
IMPLEMENTED TESTS PASSED!", "3 Goodbye!" for the piped acceptance script).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
