rust: Use Cargo to build the Rust portion

Pros: Ability to use Rust libraries from crates.io
Problems: Need to lock library versions and document their reproducible building, either via Cargo.lock or vendoring.

.gitlab-ci.yml

@@ -9,6 +9,10 @@ stages:
     - librem5
 
 before_script:
+  - apt-get -y update
+  - apt-get -y install wget ca-certificates gnupg
+  - echo "deb http://ci.puri.sm/ scratch librem5" > /etc/apt/sources.list.d/ci.list
+  - wget -O- https://ci.puri.sm/ci-repo.key | apt-key add -
   - apt-get -y update
   - apt-get -y build-dep .
 

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "rs"
+version = "0.1.0"
+
+[lib]
+name = "rs"
+path = "src/lib.rs"
+crate-type = ["staticlib"]

cargo.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+set -e
+
+export CARGO_TARGET_DIR=`pwd`
+if [ ! -z ${2} ]; then
+    OUT_PATH=`realpath "${2}"`
+fi
+
+cd $1
+cargo $3 -p rs
+
+if [ ! -z ${OUT_PATH} ]; then
+    cp "${CARGO_TARGET_DIR}"/debug/librs.a "${OUT_PATH}"
+fi

debian/control

@@ -3,6 +3,7 @@ Section: x11
 Priority: optional
 Maintainer: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
 Build-Depends:
+ cargo,
  debhelper (>= 10),
  meson (>=0.43.0),
  pkg-config,

meson.build

@@ -3,7 +3,7 @@ project(
     'c', 'rust',
     version: '1.0.10',
     license: 'GPLv3',
-    meson_version: '>=0.49.0',
+    meson_version: '>=0.51.0',
     default_options: [
         'warning_level=1',
         'buildtype=debugoptimized',

src/meson.build

@@ -56,25 +56,27 @@ deps = [
 #  dependency('libxklavier'), # FIXME remove
 ]
 
-# Replacement for eekboard-server
-rslib = static_library(
-  'rslib',
-  sources: ['lib.rs'],
-  rust_crate_type: 'staticlib'
+cargo = find_program('cargo')
+cargo_script = find_program('../cargo.sh')
+
+rslibs = custom_target(
+    'rslibs',
+    build_by_default: true,
+    build_always_stale: true,
+    output: ['librs.a'],
+    install: false,
+    command: [cargo_script, '@CURRENT_SOURCE_DIR@', '@OUTPUT@', 'build']
 )
 
-rstests = executable(
-  'rstests',
-  sources: ['lib.rs'],
-  rust_args: ['--test'],
-  install: false
+test(
+    'rstest',
+    cargo_script,
+    args: [meson.source_root(), '', 'test']
 )
 
-test('rstests', rstests)
-
 libsqueekboard = static_library('libsqueekboard',
   sources,
-  link_with: rslib,
+  link_with: [rslibs],
   include_directories: [include_directories('..'), include_directories('../eek')],
   dependencies: deps,
   c_args: [