Add build scripts

This patch adds three build scripts for the sr.ht CI:
- archlinux.yml is the main build script.  It builds the project using
  the latest stable release from rustup and executes the tests, clippy
  and rustfmt.  The build also runs the reuse tool to check compliance
  with the reuse specification and verifies that the last commit is
  signed by me.
- archlinux-msrv.yml builds and tests the project on the MSRV, currently
  Rust 1.40.0.

.builds/archlinux-msrv.yml

@@ -0,0 +1,19 @@
+# Copyright (C) 2020 Robin Krahl <robin.krahl@ireas.org>
+# SPDX-License-Identifier: CC0-1.0
+image: archlinux
+packages:
+  - rustup
+sources:
+  - https://git.sr.ht/~ireas/rusty-man
+tasks:
+  - setup: |
+      rustup set profile minimal
+      rustup default 1.40.0
+  - version: |
+      rustc -V
+  - build: |
+      cd rusty-man
+      cargo build --release
+  - test: |
+      cd rusty-man
+      cargo test

.builds/archlinux.yml

@@ -0,0 +1,36 @@
+# Copyright (C) 2020 Robin Krahl <robin.krahl@ireas.org>
+# SPDX-License-Identifier: CC0-1.0
+image: archlinux
+packages:
+  - gnupg
+  - reuse
+  - rustup
+sources:
+  - https://git.sr.ht/~ireas/rusty-man
+tasks:
+  - setup: |
+      rustup set profile minimal
+      rustup default stable
+      rustup component add rustfmt
+      rustup component add clippy
+  - version: |
+      rustc -V
+  - verify: |
+      cd rusty-man
+      curl -s "https://pgp.ireas.org/0x6D533958F070C57C.txt" | gpg --import
+      git verify-commit HEAD
+  - reuse: |
+      cd rusty-man
+      reuse lint
+  - build: |
+      cd rusty-man
+      cargo build --release
+  - test: |
+      cd rusty-man
+      cargo test
+  - clippy: |
+      cd rusty-man
+      cargo clippy -- -D warnings
+  - format: |
+      cd rusty-man
+      cargo fmt -- --check