chore(CI): Skip installing Cygwin

appveyor.yml

@@ -1,24 +1,13 @@
 # Appveyor configuration file for CI build of hiredis on Windows (under Cygwin)
 environment:
     matrix:
-        - CYG_ROOT: C:\cygwin64
-          CYG_SETUP: setup-x86_64.exe
-          CYG_MIRROR: http://cygwin.mirror.constant.com
-          CYG_CACHE: C:\cygwin64\var\cache\setup
-          CYG_BASH: C:\cygwin64\bin\bash
+        - CYG_BASH: C:\cygwin64\bin\bash
           CC: gcc
-        - CYG_ROOT: C:\cygwin
-          CYG_SETUP: setup-x86.exe
-          CYG_MIRROR: http://cygwin.mirror.constant.com
-          CYG_CACHE: C:\cygwin\var\cache\setup
-          CYG_BASH: C:\cygwin\bin\bash
+        - CYG_BASH: C:\cygwin\bin\bash
           CC: gcc
           TARGET: 32bit
           TARGET_VARS: 32bit-vars
 
-# Cache Cygwin files to speed up build
-cache:
-    - '%CYG_CACHE%'
 clone_depth: 1
 
 # Attempt to ensure we don't try to convert line endings to Win32 CRLF as this will cause build to fail
@@ -27,8 +16,6 @@ init:
 
 # Install needed build dependencies
 install:
-    - ps: 'Start-FileDownload "http://cygwin.com/$env:CYG_SETUP" -FileName "$env:CYG_SETUP"'
-    - '%CYG_SETUP% --quiet-mode --no-shortcuts --only-site --root "%CYG_ROOT%" --site "%CYG_MIRROR%" --local-package-dir "%CYG_CACHE%" --packages automake,bison,gcc-core,libtool,make,gettext-devel,gettext,intltool,pkg-config,clang,llvm > NUL 2>&1'
     - '%CYG_BASH% -lc "cygcheck -dc cygwin"'
 
 build_script: