Missing textflag.h

I'm trying to install de but get an error:
``` go
# golang.org/x/exp/shiny/driver/internal/swizzle
go/src/golang.org/x/exp/shiny/driver/internal/swizzle/swizzle_amd64.s:5:10: fatal error: textflag.h: No such file or directory
    5 | #include "textflag.h"
      |          ^~~~~~~~~~~~
compilation terminated.```