configure.py: Drop explicit import of int builtin

I can't reproduce the error that made me add this.

Reported-by: Kim Gräsman <kim.grasman@gmail.com>
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Reviewed-by: Kim Gräsman <kim.grasman@gmail.com>
Reviewed-by: Aaron Watry <awatry@gmail.com>
llvm-svn: 310968