ckpool 1.2.0

Start in the Dockerfile and inspect the build steps around configure.ac, ./autogen.sh, and ./configure. Reproduce the v1.2.0 build on the available node hardware, then verify the resulting container starts without an Illegal instruction crash loop and that miners connect successfully.

Hi @lukechilds ,

I've been testing the update to ckpool v1.2.0 for my Umbrel app Bassin first on the community app store.

As you know, Bassin on the official Umbrel App Store uses ghcr.io/getumbrel/docker-ckpool-solo for security and verified build provenance. When testing the v1.2.0 build, I ran into an Illegal instruction (SIGILL) crash loop on node hardware (e.g. Raspberry Pi / non-server CPUs). I wanted to share the root cause and tested fix with you so the official Umbrel image doesn't hit it when you update.

──────
│ Caution
│
│ ### The Bug
│
│ Building v1.2.0 on GitHub Actions caused the container to crash immediately on node startup with:
│
│ ckpool_1 | Illegal instruction

│ Note
│
│ ### Root Cause
│
│ In upstream ckpool v1.2.0, commit 6f343f3 https://bitbucket.org/ckolivas/ckpool/commits/6f343f3ba424a267a529e01e11b8c70d0bcc7239 ("Add -g to default CFLAGS and mirror
│ them in CXX") moved the default flags check to line 1 of configure.ac:
│
│ if test -z "$CFLAGS"; then
│ CFLAGS="-g -O2 -Wall -march=native"
│
│ In v1.1.1, this check was placed after AC_PROG_CC (where Autoconf had already initialized CFLAGS), so -march=native was never applied. In v1.2.0, it is evaluated first,
│ causing GCC to compile with instructions specific to the GitHub Actions cloud runner CPU. When executed on an end-user device (like a Raspberry Pi 4 or older x86 mini-
│ PC), it crashes on unsupported instructions.

│ Tip
│
│ ### The Fix
│
│ In the Dockerfile, strip -march=native and explicitly pass portable baseline flags to ./configure:
│
│ # Hack to disable cpu based optimisations for more portable builds
│ # We just make sure the cpu arch checks fail so no optimisations are enabled
│ RUN sed -i "s/host_cpu = 'x86_64'/host_cpu = 'x86_64-disabled'/" configure.ac
│ RUN sed -i "s/host_cpu = 'aarch64'/host_cpu = 'aarch64-disabled'/" configure.ac
│ + RUN sed -i "s/-march=native//g" configure.ac
│
│ # Build
│ RUN ./autogen.sh
│ - RUN ./configure
│ + RUN ./configure CFLAGS="-O2 -Wall" CXXFLAGS="-O2 -Wall"
│ RUN make -j$(nproc)
──────
I've verified this build on my node with my community app store version of bassin and miners connect smoothly and everything is rock solid.

Happy to open a PR on getumbrel/docker-ckpool-solo whenever you're ready!