Use printf instead of heredoc for cargo config — heredoc inside a
conditional RUN block confuses Docker's parser (fi becomes an unknown
instruction). The config is always written; unused linker entries are
harmless on native builds.
gcc-aarch64-linux-gnu is an x86→arm64 cross-compiler; it doesn't exist
on arm64 hosts (like the Pi). Only install cross-toolchains and set cargo
linker config when BUILDPLATFORM != TARGETPLATFORM.
Dockerfile now uses BuildKit TARGETARCH/TARGETVARIANT to pick the Rust
cross-compilation target automatically. The build stage always runs on
the host platform for speed.
Makefile provides named targets:
make up-amd64 # Mac Intel / Linux desktop
make up-arm64 # Mac M1/M2/M3, Pi 4/5 (64-bit OS)
make up-armv7 # Pi 2/3/4 (32-bit OS)
make up-armv6 # Pi Zero / Pi 1
Build hiy-server targeting aarch64-unknown-linux-musl so the binary
has no glibc dependency at all, making the runtime image irrelevant
to glibc version mismatches. Uses rustls (already in Cargo.toml) so
no OpenSSL vendoring needed. SQLite is bundled by sqlx.
rust:1.77-slim has drifted to a newer Debian base with glibc 2.39,
but debian:bookworm-slim only has glibc 2.36, causing a GLIBC_2.39
not found error at runtime. Pinning to the explicit bookworm variant
keeps both stages on the same glibc version.
