Add basic meson.build for rust project

While the project compiles OK with `cargo build`, it does not compile
with meson. See https://github.com/mesonbuild/meson/issues/3632

.gitignore

@@ -1,2 +1,3 @@
 /target
 **/*.rs.bk
+build

meson.build

@@ -0,0 +1,6 @@
+project('meson-rust', ['rust'])
+
+executable('main', [
+  'src/main.rs',
+  'src/foo.rs'
+  ])