Hide signals tests behind a build tag

Testing signals requires additional executables to be available in the $PATH
and can intermittently fail as well.

Add a build tag, which means these specific tests will only run when requested.

Closes #780

Taskfile.yml

@@ -65,10 +65,16 @@ tasks:
 
   test:
     desc: Runs test suite
-    deps: [install, sleepit:build]
+    deps: [install]
     cmds:
       - go test {{catLines .GO_PACKAGES}}
 
+  test:signals:
+    desc: Runs test suite with signals tests included
+    deps: [install, sleepit:build]
+    cmds:
+      - go test {{catLines .GO_PACKAGES}} -tags signals
+
   test-release:
     desc: Tests release process without publishing
     cmds:

signals_test.go

@@ -1,5 +1,5 @@
-//go:build !windows
-// +build !windows
+//go:build signals
+// +build signals
 
 // This file contains tests for signal handling on Unix.
 // Based on code from https://github.com/marco-m/timeit