Change license check to use a better action

I had implemented this myself previously, because I didn't think this
project could do anything more than Apache, but I was wrong. This is
much cleaner.

Author: steveklabnik

.github/workflows/license-check.yml

@@ -0,0 +1,9 @@
+name: license-check
+on: pull_request
+jobs:
+  license:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Check License Header
+      uses: apache/skywalking-eyes@main  

.github/workflows/license.yml

@@ -0,0 +1,12 @@
+header:
+  license:
+    spdx-id: MPL-2.0
+
+    content: |
+      This Source Code Form is subject to the terms of the Mozilla Public
+      License, v. 2.0. If a copy of the MPL was not distributed with this
+      file, You can obtain one at https://mozilla.org/MPL/2.0/.
+  paths:
+    - '**/*.rs'
+
+  comment: on-failure

.licenserc.yaml

@@ -17,7 +17,6 @@ mod elf;
 mod flash;
 mod gdb;
 mod humility;
-mod license;
 mod task_slot;
 mod test;
 
@@ -123,9 +122,6 @@ enum Xtask {
         /// Path to task executable
         task_bin: PathBuf,
     },
-
-    /// Check that all .rs files have the MPL header
-    LicenseCheck,
 }
 
 #[derive(Clone, Debug, Deserialize)]
@@ -416,11 +412,6 @@ fn main() -> Result<()> {
         Xtask::TaskSlots { task_bin } => {
             task_slot::dump_task_slot_table(&task_bin)?;
         }
-        Xtask::LicenseCheck => {
-            if !license::check()? {
-                std::process::exit(1);
-            }
-        }
     }
 
     Ok(())