new computer ./configure doesn't fail on LEX absence

[Valentin Tolmer]

Hello,

After setting up bison on a new computer, and getting a successful 
bootstrap and configure, I try to make, and it fails with an error 1 (no 
more details) on LEX src/scan-code.c (the first lex file to compile). 
After rummaging a bit, I realize that I don't have flex installed, so I 
install it, but no cigar.
After another ./configure, though, the build is successful.
Any thoughts? I think the flex absence should be a configure fail if it 
prevents compilation.

Valentin Tolmer