/home/borist/builds/llvm/lib/AsmParser/Lexer.l: In function 'int
Could it be a problem with my version of gcc (V4.2.2) on Linux x86_64?
No. These files were removed from the svn, however, they were used to
generate source files and such generated files still alive in your tree.
Remove Lexer.cpp and Lexer.h (same applies for tablegen).
You can use "svn status" command to check for extra files.