builds/nixos.yml: replace archlinux build

.builds/nixos.yml

@@ -0,0 +1,25 @@
+---
+image: nixos/unstable
+packages:
+ - nixos.dmd
+ - nixos.curl
+ - nixos.gnumake
+ - nixos.ldc
+environment:
+  NIX_CONFIG: "experimental-features = nix-command flakes"
+sources:
+  - "https://git.sr.ht/~jeremy/esv"
+tasks:
+  - build-dmd: |
+      cd esv
+      ./configure -c dmd
+      make all clean
+  - build-ldc: |
+      cd esv
+      ./configure -c ldc2
+      make
+  - install: |
+      nix profile install ./esv
+  - test: |
+      # very basic test :)
+      esv Matthew 5-7 >/dev/null