Ignoring ffi-1.12.2 because its extensions are not built. Try: gem pristine ffi --version 1.12.2

升级到maxOS Big Sur和Xcode12.3之后，执行pod install总是报错

Ignoring ffi-1.12.2 because its extensions are not built. Try: gem pristine ffi --version 1.12.2
提示我们执行

gem pristine ffi --version 1.12.2

执行之后又会报错

ERROR:  While executing gem ... (Gem::FilePermissionError)
 You don't have write permissions for the /Library/Ruby/Gems/2.6.0 directory.
说没有写入权限。
既然如此，就加上权限，继续执行

sudo gem pristine ffi --version 1.12.2
终端输出日志

Restoring gems to pristine condition...
Building native extensions. This could take a while...
Restored ffi-1.12.2

执行完之后就好了。
类似的错误，都可以通过这种方式解决

Ignoring RedCloth-4.3.2 because its extensions are not built.  Try: gem pristine RedCloth --version 4.3.2
Ignoring bluecloth-2.2.0 because its extensions are not built.  Try: gem pristine bluecloth --version 2.2.0
Ignoring commonmarker-0.20.2 because its extensions are not built.  Try: gem pristine commonmarker --version 0.20.2
Ignoring eventmachine-1.2.7 because its extensions are not built.  Try: gem pristine eventmachine --version 1.2.7
Ignoring ffi-1.13.1 because its extensions are not built.  Try: gem pristine ffi --version 1.13.1
Ignoring ffi-1.12.2 because its extensions are not built.  Try: gem pristine ffi --version 1.12.2
Ignoring http-parser-1.2.2 because its extensions are not built.  Try: gem pristine http-parser --version 1.2.2
Ignoring http_parser.rb-0.6.0 because its extensions are not built.  Try: gem pristine http_parser.rb --version 0.6.0
Ignoring kgio-2.11.3 because its extensions are not built.  Try: gem pristine kgio --version 2.11.3
Ignoring nio4r-2.5.4 because its extensions are not built.  Try: gem pristine nio4r --version 2.5.4
Ignoring nio4r-2.5.2 because its extensions are not built.  Try: gem pristine nio4r --version 2.5.2
Ignoring nokogiri-1.10.10 because its extensions are not built.  Try: gem pristine nokogiri --version 1.10.10
Ignoring puma-5.1.0 because its extensions are not built.  Try: gem pristine puma --version 5.1.0
Ignoring puma-4.3.5 because its extensions are not built.  Try: gem pristine puma --version 4.3.5
Ignoring puma-3.12.6 because its extensions are not built.  Try: gem pristine puma --version 3.12.6
Ignoring puma-3.12.0 because its extensions are not built.  Try: gem pristine puma --version 3.12.0
Ignoring raindrops-0.19.1 because its extensions are not built.  Try: gem pristine raindrops --version 0.19.1
Ignoring rdiscount-2.2.0.2 because its extensions are not built.  Try: gem pristine rdiscount --version 2.2.0.2
Ignoring redcarpet-3.5.0 because its extensions are not built.  Try: gem pristine redcarpet --version 3.5.0
Ignoring therubyracer-0.12.3 because its extensions are not built.  Try: gem pristine therubyracer --version 0.12.3
Ignoring unf_ext-0.0.7.7 because its extensions are not built.  Try: gem pristine unf_ext --version 0.0.7.7
Ignoring unicorn-5.7.0 because its extensions are not built.  Try: gem pristine unicorn --version 5.7.0
Ignoring websocket-driver-0.7.3 because its extensions are not built.  Try: gem pristine websocket-driver --version 0.7.3
Ignoring yajl-ruby-1.4.1 because its extensions are not built.  Try: gem pristine yajl-ruby --version 1.4.1
Ignoring RedCloth-4.3.2 because its extensions are not built.  Try: gem pristine RedCloth --version 4.3.2
Ignoring bluecloth-2.2.0 because its extensions are not built.  Try: gem pristine bluecloth --version 2.2.0
Ignoring commonmarker-0.20.2 because its extensions are not built.  Try: gem pristine commonmarker --version 0.20.2
Ignoring eventmachine-1.2.7 because its extensions are not built.  Try: gem pristine eventmachine --version 1.2.7
Ignoring ffi-1.13.1 because its extensions are not built.  Try: gem pristine ffi --version 1.13.1
Ignoring ffi-1.12.2 because its extensions are not built.  Try: gem pristine ffi --version 1.12.2
Ignoring http-parser-1.2.2 because its extensions are not built.  Try: gem pristine http-parser --version 1.2.2
Ignoring http_parser.rb-0.6.0 because its extensions are not built.  Try: gem pristine http_parser.rb --version 0.6.0
Ignoring kgio-2.11.3 because its extensions are not built.  Try: gem pristine kgio --version 2.11.3
Ignoring nio4r-2.5.4 because its extensions are not built.  Try: gem pristine nio4r --version 2.5.4
Ignoring nio4r-2.5.2 because its extensions are not built.  Try: gem pristine nio4r --version 2.5.2
Ignoring nokogiri-1.10.10 because its extensions are not built.  Try: gem pristine nokogiri --version 1.10.10
Ignoring puma-5.1.0 because its extensions are not built.  Try: gem pristine puma --version 5.1.0
Ignoring puma-4.3.5 because its extensions are not built.  Try: gem pristine puma --version 4.3.5
Ignoring puma-3.12.6 because its extensions are not built.  Try: gem pristine puma --version 3.12.6
Ignoring puma-3.12.0 because its extensions are not built.  Try: gem pristine puma --version 3.12.0
Ignoring raindrops-0.19.1 because its extensions are not built.  Try: gem pristine raindrops --version 0.19.1
Ignoring rdiscount-2.2.0.2 because its extensions are not built.  Try: gem pristine rdiscount --version 2.2.0.2
Ignoring redcarpet-3.5.0 because its extensions are not built.  Try: gem pristine redcarpet --version 3.5.0
Ignoring therubyracer-0.12.3 because its extensions are not built.  Try: gem pristine therubyracer --version 0.12.3
Ignoring unf_ext-0.0.7.7 because its extensions are not built.  Try: gem pristine unf_ext --version 0.0.7.7
Ignoring unicorn-5.7.0 because its extensions are not built.  Try: gem pristine unicorn --version 5.7.0
Ignoring websocket-driver-0.7.3 because its extensions are not built.  Try: gem pristine websocket-driver --version 0.7.3
Ignoring yajl-ruby-1.4.1 because its extensions are not built.  Try: gem pristine yajl-ruby --version 1.4.1