try store mounted read-only

- `--store` as per
https://blog.kotatsu.dev/posts/2023-04-21-woodpecker-nix-caching/
- `--eval-store` as per
https://kevincox.ca/2022/01/02/nix-in-docker-caching/

mount store

rm kvm

.woodpecker/cd.yaml

@@ -8,12 +8,14 @@ when:
 steps:
   - name: build
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
       - |
         mkdir -p ~/.ssh
         echo "$CD_SSH_KEY" > ~/.ssh/id_ed25519
         chmod 600 ~/.ssh/id_ed25519
-      - nix-shell --run 'eval "$(ssh-agent -s)" && ssh-add ~/.ssh/id_ed25519 && ssh-agent -s && SHELL=$(which bash) nixops4 apply -v default'
+      - nix-shell --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --run 'eval "$(ssh-agent -s)" && ssh-add ~/.ssh/id_ed25519 && ssh-agent -s && SHELL=$(which bash) nixops4 apply -v default'
     environment:
       CD_SSH_KEY:
         from_secret: cd_ssh_key

.woodpecker/check-data-model.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-data-model
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix-shell --run 'nix-unit ./deployment/data-model-test.nix'
+      - nix-shell --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --run 'nix-unit ./deployment/data-model-test.nix'

.woodpecker/check-deployment-basic.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-deployment-basic
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-basic -L
+      - nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-basic -L

.woodpecker/check-deployment-cli.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-deployment-cli
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-cli -L
+      - nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-cli -L

.woodpecker/check-deployment-panel.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-deployment-panel
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-panel -L
+      - nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.deployment-panel -L

.woodpecker/check-mastodon.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-mastodon
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.test-mastodon-service -L
+      - nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.test-mastodon-service -L

.woodpecker/check-panel.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-panel
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix-build -A tests.panel
+      - nix-build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt -A tests.panel

.woodpecker/check-peertube.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-peertube
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.test-peertube-service -L
+      - nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.test-peertube-service -L

.woodpecker/check-pre-commit.yaml

@@ -9,5 +9,7 @@ when:
 steps:
   - name: check-pre-commit
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix-build -A tests
+      - nix-build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt -A tests

.woodpecker/check-resources.yaml

@@ -14,20 +14,22 @@ when:
 steps:
   - name: check-resources
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
       - echo ==================== [ VM Options ] ====================
       - |
         set -euC
-        machines=$(nix eval --impure --raw --expr 'with builtins; toString (attrNames (getFlake (toString ./.)).vmOptions)')
+        machines=$(nix eval --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' --impure --raw --expr 'with builtins; toString (attrNames (getFlake (toString ./.)).vmOptions)')
         for machine in $machines; do
           echo ~~~~~~~~~~~~~~~~~~~~~: $machine :~~~~~~~~~~~~~~~~~~~~~
-          nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.vmOptions-$machine
+          nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.vmOptions-$machine
         done
       - echo ==================== [ NixOS Configurations ] ====================
       - |
         set -euC
-        machines=$(nix eval --impure --raw --expr 'with builtins; toString (attrNames (getFlake (toString ./.)).nixosConfigurations)')
+        machines=$(nix eval --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' --impure --raw --expr 'with builtins; toString (attrNames (getFlake (toString ./.)).nixosConfigurations)')
         for machine in $machines; do
           echo ~~~~~~~~~~~~~~~~~~~~~: $machine :~~~~~~~~~~~~~~~~~~~~~
-          nix build --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.nixosConfigurations-$machine
+          nix build --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --extra-experimental-features 'nix-command flakes' .#checks.x86_64-linux.nixosConfigurations-$machine
         done

.woodpecker/update.yaml

@@ -8,8 +8,10 @@ when:
 steps:
   - name: lockfile
     image: nixos/nix
+    volumes:
+      - /nix:/mnt/nix:ro
     commands:
-      - nix-shell --run "npins --verbose update"
+      - nix-shell --eval-store local --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt --run "npins --verbose update"
       # - name: Create PR
       #   uses: https://github.com/KiaraGrouwstra/gitea-create-pull-request@f9f80aa5134bc5c03c38f5aaa95053492885b397
       #   with: