您好我尝试安装watir-classic但我收到以下错误
我的系统配置 Windows 7
ruby 1.8.7
Building native extensions. This could take a while...
ERROR: Error installing watir-classic:
ERROR: Failed to build gem native extension.
D:/Ruby_version/bin/ruby.exe extconf.rb
checking for ffi.h... no
checking for ffi.h in /usr/local/include,/usr/include/ffi... no
checking for rb_thread_blocking_region()... no
checking for rb_thread_call_with_gvl()... no
checking for rb_thread_call_without_gvl()... no
checking for ffi_prep_cif_var()... no
creating extconf.h
creating Makefile
nmake
'nmake' is not recognized as an internal or external command,
operable program or batch file.