% ../llvm/configure
[skipped]
checking for llvm-gcc... no
checking for llvm-g++... no
checking tool compatibility... configure: error: gcc 3.x required, but you have
a lower version

% gcc --version
gcc (GCC) 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)
Copyright (C) 2004 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

% gcc --version | head -n 1 | awk '{print $NF;}'
0.125)

I deleted this check, proceeded the build process, and everything was fine.

configure, 1.196

24843: if test "$GCC" = "yes"
24844: then
24845:   gccmajor=`$CC --version | head -n 1 | awk '{print $NF;}' | cut -d. -f1`
24846:   if test "$gccmajor" -lt "3"
24847:   then
24848:     { { echo "$as_me:$LINENO: error: gcc 3.x required, but you have a
lower version" >&5
24849: echo "$as_me: error: gcc 3.x required, but you have a lower version" >&2;}
24850:    { (exit 1); exit 1; }; }
24851:   fi
24852: fi

FIXED.
Patches here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050725/027250.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050725/027251.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050725/027252.html