Retry download cygwin setup 4x with curl

-m 600 means don't spend more than 10 minutes (600 seconds) see curl manual https://curl.haxx.se/docs/manpage.html
This was taken from appveyor docs https://www.appveyor.com/docs/how-to/download-file/

Author: nicolas-cellier-aka-nice

.appveyor.yml

@@ -113,8 +113,8 @@ cache:
   - .thirdparty-cache
 
 install:
-  - ps: 'Start-FileDownload "http://cygwin.com/setup-x86.exe" -FileName "setup-x86.exe"'
-  - ps: 'Start-FileDownload "http://cygwin.com/setup-x86_64.exe" -FileName "setup-x86_64.exe"'
+  - 'curl -fsS --retry 4 - m 600 -o "setup-x86.exe" "http://cygwin.com/setup-x86.exe" '
+  - 'curl -fsS --retry 4 - m 600 -o "setup-x86_64.exe" "http://cygwin.com/setup-x86_64.exe" '
   - '%CYG_SETUP% -dgnqNO -R "%CYG_ROOT%" -s "%CYG_MIRROR%" -l "%CYG_ROOT%\var\cache\setup" -P mingw64-%MINGW_ARCH%-gcc-core,mingw64-%MINGW_ARCH%-gcc-g++,mingw64-%MINGW_ARCH%-headers,mingw64-%MINGW_ARCH%-runtime,zip,mingw64-%MINGW_ARCH%-clang,mingw64-%MINGW_ARCH%-openssl,libiconv-devel,libglib2.0-devel,perl,mingw64-%MINGW_ARCH%-zlib,make,cmake,wget,mingw64-%MINGW_ARCH%-win-iconv'
 
 # Cygwin build script