Add support for Rust code in DDNet

The glue is done using the [cxx crate](https://cxx.rs/) on the Rust
side.

As a proof-of-concept, only a small console command (`rust_version`)
printing the currently used Rust version was added.

You can generate and open the Rust documentation using
`DDNET_TEST_NO_LINK=1 cargo doc --open`.

You can run the Rust tests using `cmake --build <build dir> --target
run_rust_tests`, they're automatically included in the `run_tests`
target as well.

Rust tests don't work on Windows in debug mode on Windows because Rust
cannot currently link with the debug version of the C stdlib on Windows:
rust-lang/rust#39016.

---

The stuff in `src/rust-bridge` is generated using
```
cxxbridge src/engine/shared/rust_version.rs --output src/rust-bridge/engine/shared/rust_version.cpp --output src/rust-bridge/engine/shared/rust_version.h
cxxbridge src/engine/console.rs --output src/rust-bridge/cpp/console.cpp --output src/rust-bridge/cpp/console.h
```

.cargo/config.toml

@@ -0,0 +1,2 @@
+[target.'cfg(target_env = "msvc")']
+rustflags = ["-C", "target-feature=+crt-static"]

.github/workflows/build.yaml

@@ -25,10 +25,9 @@ jobs:
           cmake-path: /usr/bin/
           cmake-args: -G Ninja -DTEST_MYSQL=ON
           cmake-init-env: CXXFLAGS=-Werror
+          gtest-env: GTEST_FILTER=-*SQLite*
           package-file: "*-linux_x86_64.tar.xz"
           fancy: false
-          env:
-            GTEST_FILTER: -*SQLite*
         - os: macOS-latest
           cmake-args: -G Ninja
           cmake-init-env: CXXFLAGS=-Werror
@@ -55,6 +54,7 @@ jobs:
     - name: Prepare Linux (non-fancy)
       if: ${{ contains(matrix.os, 'ubuntu') && !matrix.fancy }}
       run: |
+        rustup default 1.48.0
         sudo rm -rf /var/lib/mysql/ /var/run/mysqld
         sudo mkdir /var/lib/mysql/ /var/run/mysqld/
         sudo chown mysql:mysql /var/lib/mysql/ /var/run/mysqld/
@@ -93,48 +93,41 @@ jobs:
         sudo rm -rf /Library/Developer/CommandLineTools
 
     - name: Build in debug mode
-      env: ${{ matrix.env }}
       run: |
         mkdir debug
         cd debug
         ${{ matrix.cmake-path }}cmake -E env ${{ matrix.cmake-init-env }} ${{ matrix.cmake-path }}cmake ${{ matrix.cmake-args }} -DCMAKE_BUILD_TYPE=Debug -Werror=dev -DDOWNLOAD_GTEST=ON -DDEV=ON -DCMAKE_RUNTIME_OUTPUT_DIRECTORY_DEBUG=. ..
         ${{ matrix.cmake-path }}cmake --build . --config Debug --target everything ${{ matrix.build-args }}
 
     - name: Test debug
-      env: ${{ matrix.env }}
       run: |
         cd debug
-        ${{ matrix.cmake-path }}cmake --build . --config Debug --target run_tests ${{ matrix.build-args }}
+        ${{ matrix.cmake-path }}cmake -E env ${{ matrix.gtest-env }} ${{ matrix.cmake-path }}cmake --build . --config Debug --target run_tests ${{ matrix.build-args }}
 
     - name: Run debug server
-      env: ${{ matrix.env }}
       run: |
         cd debug
         ./DDNet-Server shutdown
 
     - name: Build in release mode
-      env: ${{ matrix.env }}
       run: |
         mkdir release
         cd release
         ${{ matrix.cmake-path }}cmake -E env ${{ matrix.cmake-init-env }} ${{ matrix.cmake-path }}cmake ${{ matrix.cmake-args }} -DCMAKE_BUILD_TYPE=Release -Werror=dev -DDOWNLOAD_GTEST=ON -DCMAKE_RUNTIME_OUTPUT_DIRECTORY_RELEASE=. ..
         ${{ matrix.cmake-path }}cmake --build . --config Release --target everything ${{ matrix.build-args }}
 
     - name: Test release
-      env: ${{ matrix.env }}
       run: |
         cd release
-        ${{ matrix.cmake-path }}cmake --build . --config Release --target run_tests ${{ matrix.build-args }}
+        ${{ matrix.cmake-path }}cmake -E env ${{ matrix.gtest-env }} ${{ matrix.cmake-path }}cmake --build . --config Release --target run_tests ${{ matrix.build-args }}
 
     - name: Run release server
-      env: ${{ matrix.env }}
       run: |
         cd release
         ./DDNet-Server shutdown
 
     - name: Build headless client
       if: contains(matrix.os, 'ubuntu-latest')
-      env: ${{ matrix.env }}
       run: |
         mkdir headless
         cd headless
@@ -178,7 +171,6 @@ jobs:
 
     - name: Build in release mode with debug info and all features on
       if: matrix.fancy
-      env: ${{ matrix.env }}
       run: |
         mkdir fancy
         cd fancy
@@ -187,14 +179,13 @@ jobs:
 
     - name: Test fancy
       if: matrix.fancy
-      env: ${{ matrix.env }}
       run: |
+        find /usr/lib/ -name '*libwebsockets*'
         cd fancy
-        ${{ matrix.cmake-path }}cmake --build . --config RelWithDebInfo --target run_tests ${{ matrix.build-args }}
+        ${{ matrix.cmake-path }}cmake -E env ${{ matrix.gtest-env }} ${{ matrix.cmake-path }}cmake --build . --config RelWithDebInfo --target run_tests ${{ matrix.build-args }}
 
     - name: Run fancy server
       if: matrix.fancy
-      env: ${{ matrix.env }}
       run: |
         cd fancy
         ./DDNet-Server shutdown

.github/workflows/rust.yml

@@ -0,0 +1,42 @@
+name: Check Rust
+
+on:
+  push:
+    branches-ignore:
+      - staging.tmp
+      - trying.tmp
+      - staging-squash-merge.tmp
+  pull_request:
+
+jobs:
+  rustdoc:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Run Rustdoc
+      run: |
+        RUSTDOCFLAGS=-Dwarnings DDNET_TEST_NO_LINK=1 cargo doc
+
+  rustfmt:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Run Rustfmt
+      run:
+        cargo fmt -- --check
+
+  cargo-deny:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        checks:
+          - advisories
+          - bans licenses sources
+
+    continue-on-error: ${{ matrix.checks == 'advisories' }}
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: EmbarkStudios/cargo-deny-action@v1
+      with:
+        command: check ${{ matrix.checks }}

.gitignore

@@ -11,6 +11,7 @@ bundle/
 .DS_Store
 .ninja_deps
 .ninja_log
+CACHEDIR.TAG
 CMakeCache.txt
 CMakeFiles
 CMakeSettings*
@@ -20,10 +21,12 @@ CTestTestfile.cmake
 Debug
 Makefile
 Release
+SAN.*
 _CPack_Packages/
 build.ninja
 checksummed_*
 cmake_install.cmake
+debug
 gmock.pc
 gmock_main.pc
 googletest-build/
@@ -34,8 +37,8 @@ gtest_main.pc
 install_manifest*.txt
 ninja_package
 pack_*/
+release
 rules.ninja
-SAN.*
 testrunner\[1\]_include.cmake
 vulkan_shaders_sha256.txt