title: Trouble building gcc 4.6: undefined reference to `yylex'
body: <p>I'm trying to build gcc 4.6, but I'm getting some linker errors that look like it means bison or flex isn't getting linked to. When the makefile issues this command:</p>
  
  <pre><code>gcc   -g -fkeep-inline-functions -DIN_GCC   -W -Wall -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Wold-style-definition -Wc++-compat -fno-common  -DHAVE_CONFIG_H -DGENERATOR_FILE  -o build/gengtype \
          build/gengtype.o build/errors.o build/gengtype-lex.o build/gengtype-parse.o build/version.o ../../build-x86_64-unknown-linux-gnu/libiberty/libiberty.a
  </code></pre>
  
  <p>It tells me:</p>
  
  <pre><code>/home/chris/code/gcc/trunk/host-x86_64-unknown-linux-gnu/gcc/../.././gcc/gengtype.c:960: undefined reference to `lexer_line'
  ... undefined reference to `yylex'
  ... undefined reference to `yybegin'
  ... undefined reference to `yyend'
  </code></pre>
  
  <p>I've installed Flex and Bison, and even tried several Bison variants with the same result. Does anybody know what else this might mean?</p>