cleanup

* cleanup Cargo.toml

* exclude backend from windows build

* remove env include in windows build

* remove Backend from windows build

* fix compiler warning

Cargo.lock

@@ -237,7 +237,6 @@ dependencies = [
  "serde",
  "serde_derive",
  "tempfile",
- "threadpool",
  "toml",
  "trust-dns-resolver",
  "wayland-client",
@@ -632,15 +631,6 @@ dependencies = [
  "syn",
 ]
 
-[[package]]
-name = "threadpool"
-version = "1.8.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d050e60b33d41c19108b32cea32164033a9013fe3b46cbd4457559bfbf77afaa"
-dependencies = [
- "num_cpus",
-]
-
 [[package]]
 name = "tinyvec"
 version = "1.6.0"