Install unreal engine on external hard drive with ubuntu

Hi as the question explains, I’d like to install unreal engine on an external SSD hard drive because my current ubuntu pc doesn’t have enough memory space. Please help me, I’m stuck after compiling all the ressources using git and running ./Setup.sh and then ./GenerateProjectFiles.sh fails saying :
after a lot of failed to create symbol link
error CS0006: Metadata file System.dll' could not be found error CS0006: Metadata file System.Core.dll’ could not be found
ERROR: Unable to compile source files.

Thank you