builds: initialise

Initialise builds.sr.ht CI to build for Alpine Linux, Arch Linux and
OpenBSD. Building for Arch will also test the Nix flake builds.

.builds/archlinux.yml

@@ -0,0 +1,28 @@
+---
+image: archlinux
+packages:
+  - clang
+  - nix
+sources:
+  - "https://git.sr.ht/~jeremy/callisto"
+tasks:
+  - prepare: |
+      printf 'experimental-features = nix-command flakes\n' \
+        | sudo tee -a /etc/nix/nix.conf
+      sudo systemctl start nix-daemon
+      sudo usermod -aG nix-users build
+  - build-clang: |
+      cd callisto
+      ./configure -c clang
+      make
+      make clean
+  - build-gcc: |
+      cd callisto
+      ./configure -c gcc
+      make
+  - install: |
+      sudo make -Ccallisto install
+  - test: |
+      csto callisto/test.lua
+  - flake: |
+      nix build ./callisto