Small fixes to enable LTO compilation (#3418)
Small fixes to enable LTO compilation (#3418)

Small fixes to enable LTO compilation

To do this in racket/src:
  ./configure CFLAGS="-O3 -march=native -flto"
              LDFLAGS="-O3 -march=native -flto"
              --prefix=...

One fix deals with variable `errnum` that might be used uninitialized.
The other is to ensure that `boot_file_data` is marked as used
otherwise, it is removed by LTO and ends up crashing build
in `embed-boot.rkt`.
mflatt/ChezScheme,mflatt/ChezScheme,mflatt/ChezScheme