ci(nix): switch from DeterminateSystems/nix-installer-action to cachix/install-nix-action

Determinate Systems GitHub action
installs Nix version from Determinate Systems
and Determinate Nix Installer has
dropped support for installing upstream Nix:
https://determinate.systems/blog/installer-dropping-upstream/

This commit switches to upstream Nix
to avoid accidentally depending on any features
of Determinate Nix.

Author: link2xt

.github/workflows/deltachat-rpc-server.yml

@@ -34,7 +34,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
 
       - name: Build deltachat-rpc-server binaries
         run: nix build .#deltachat-rpc-server-${{ matrix.arch }}-linux
@@ -58,7 +58,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
 
       - name: Build deltachat-rpc-server binaries
         run: nix build .#deltachat-rpc-server-${{ matrix.arch }}
@@ -109,7 +109,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
 
       - name: Build deltachat-rpc-server binaries
         run: nix build .#deltachat-rpc-server-${{ matrix.arch }}-android
@@ -136,7 +136,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
 
       - name: Download Linux aarch64 binary
         uses: actions/download-artifact@v5

.github/workflows/nix.yml

@@ -25,7 +25,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - run: nix fmt flake.nix -- --check
 
   build:
@@ -84,7 +84,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - run: nix build .#${{ matrix.installable }}
 
   build-macos:
@@ -104,5 +104,5 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - run: nix build .#${{ matrix.installable }}

.github/workflows/repl.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           show-progress: false
           persist-credentials: false
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - name: Build
         run: nix build .#deltachat-repl-win64
       - name: Upload binary

.github/workflows/upload-docs.yml

@@ -36,7 +36,7 @@ jobs:
           show-progress: false
           persist-credentials: false
           fetch-depth: 0 # Fetch history to calculate VCS version number.
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - name: Build Python documentation
         run: nix build .#python-docs
       - name: Upload to py.delta.chat
@@ -55,7 +55,7 @@ jobs:
           show-progress: false
           persist-credentials: false
           fetch-depth: 0 # Fetch history to calculate VCS version number.
-      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31
       - name: Build C documentation
         run: nix build .#docs
       - name: Upload to c.delta.chat