grub2 boot root-on-zfs errors

[Beeblebrox]

I did not have time to play around with trunk/grub for a while so was
not able to follow-up on the discussion. Continuing from last month's
topic:

> Flex version 2.5.4 is less than 2.3.35.
2.5 is > 2.3
The problem was answered by the port maintainer for me:
"FreeBSD includes an older version of Flex in the base system. You
will need that the compilation should use the version installed in
/usr/local/bin instead. Either by putting this directory in your $PATH
earlier than /usr/bin or by specifying the location on the command
line."
Was solved by editing $PATH to look in /usr/local/bin first.

The new problem is that after autogen and configure complete without
errors, gmake fails (gcc version is 4.6):
gcc -DHAVE_CONFIG_H -I.   -Wall -W -I./include -DGRUB_UTIL=1
-DGRUB_LIBDIR=\"/usr/local/lib/grub\"
-DLOCALEDIR=\"/usr/local/share/locale\"
-DGRUB_FILE=\"grub_script.yy.c\" -I. -I. -I. -I. -I./include
-I./include -I./grub-core/lib/libgcrypt-grub/include
-I./grub-core/lib/libgcrypt-grub/src/  -I./grub-core/lib/minilzo
-I./grub-core/lib/xzembed -DMINILZO_HAVE_CONFIG_H
-I/usr/local/include  -Wall -W -Wshadow -Wold-style-definition
-Wpointer-arith -Wundef -Wextra -Wattributes -Wcast-align
-Wchar-subscripts -Wcomment -Wdeprecated-declarations
-Wdisabled-optimization -Wdiv-by-zero -Wendif-labels -Wfloat-equal
-Wformat-extra-args -Wformat-security -Wformat-y2k -Wimplicit
-Wimplicit-function-declaration -Wimplicit-int -Winit-self
-Wint-to-pointer-cast -Winvalid-pch -Wmain -Wmissing-braces
-Wmissing-field-initializers -Wmissing-format-attribute -Wmultichar
-Wnonnull -Woverflow -Wparentheses -Wpointer-arith
-Wpointer-to-int-cast -Wreturn-type -Wsequence-point -Wshadow
-Wsign-compare -Wstrict-aliasing -Wswitch -Wtrigraphs -Wundef
-Wunknown-pragmas -Wunused -Wunused-function -Wunused-label
-Wunused-parameter -Wunused-value  -Wunused-variable -Wvariadic-macros
-Wvolatile-register-var -Wwrite-strings -Wnested-externs
-Wstrict-prototypes -Wpointer-sign -Werror  -fno-builtin -Wno-undef
             -MT libgrubmods_a-grub_script.yy.o -MD -MP -MF
.deps-util/libgrubmods_a-grub_script.yy.Tpo -c -o
libgrubmods_a-grub_script.yy.o `test -f 'grub_script.yy.c' || echo
'./'`grub_script.yy.c
cc1: warnings being treated as errors
grub_script.yy.c: In function 'yy_scan_bytes':
grub_script.yy.c:2298: warning: comparison between signed and unsigned
gmake[2]: *** [libgrubmods_a-grub_script.yy.o] Error 1
gmake[2]: Leaving directory `/asp/git/grub'
gmake[1]: *** [all-recursive] Error 1
gmake[1]: Leaving directory `/asp/git/grub'
gmake: *** [all] Error 2

Any ideas how to move forward? I assume I'm on the right branch:
bzr info -v .
Standalone tree (format: 2a)
Related branches:   parent branch:
http://bzr.savannah.gnu.org/r/grub/trunk/grub/
Branch history:       5210 revisions       1946 days old
   first revision: Wed 2008-07-02 19:22:35 +0000
  latest revision: Sat 2013-09-28 03:06:04 +0200
Repository:        7726 revisions