Add a RISC-V subsection to docs/install.md inside 'Building from source',
between the existing MIPS and FreeBSD sections, covering:
- Target selection table (RISCV64_GENERIC / RISCV64_ZVL128B /
RISCV64_ZVL256B / C910V / x280) and what each is for.
- The general property that GENERIC / ARCH_GENERIC targets across
all architectures map to the non-vectorized plain-C reference
path, with the Makefile.riscv64 scalar -march override noted as
the RISC-V-specific compounding factor.
- GCC 14+ requirement for the ZVL targets on current OpenBLAS
releases (GCC 13 does not implement the __riscv_vsseg* intrinsics
used by the _rvv.c kernels and falls back to scalar silently,
detectable only by disassembly).
- Reference objdump-based verification command and expected
opcode-count range for a correct RISCV64_ZVL128B build.
README.md now keeps a single one-line pointer to the new install.md
section at the spot where users encounter the RISC-V build commands,
so the signposting is preserved without bloating the page that GitHub
renders by default.
v2 of this PR, addresses review feedback from @martin-frbg on
relocation and on the broader GENERIC framing.
Co-authored-by: Vaibhav805 <Vaibhav805@users.noreply.github.com>
