Add a function for splitting search paths

src/common/process.h

@@ -41,6 +41,12 @@
  */
 bool pid_running(pid_t pid);
 
+/**
+ * Split a `PATH`-like environment variable on colons. These environment
+ * variables don't support escaping, which makes this a lot simpler.
+ */
+std::vector<ghc::filesystem::path> split_path(const std::string_view& path_env);
+
 /**
  * Helper to create an `environ`-like environment object for passing to the
  * `exec*e()` family of functions.