Fix appveyor PATH

appveyor.yml

@@ -17,6 +17,7 @@ install:
   - git submodule update --init
   - appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
   - rustup-init.exe --default-host x86_64-pc-windows-msvc --default-toolchain nightly -y
+  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
   - if NOT "%TARGET%" == "x86_64-pc-windows-msvc" rustup target add %TARGET%
 
   # Use the system msys