I am having problems building current on i386 with gcc4 using build.sh

Under GCC 3 (/etc/mk.conf empty) 

./build.sh -U -T ../tools -O ../obj  tools    
then
./build.sh -U -T ../tools -O ../obj  kernel=GENERIC  

compiles everything fine.

clearing out /usr/obj & /usr/tools and setting HAVE_GCC=4 in /etc/mk.conf 

./build.sh -U -T ../tools -O ../obj  tools    

works fine and builds the tools, but then 

./build.sh -U -T ../tools -O ../obj  kernel=GENERIC 

fails at:

#   compile  GENERIC/aac.o
/usr/src/../tools/bin/i386--netbsdelf-gcc -ffreestanding -O2 -Werror -Wall 
-Wno-main -Wno-format-zero-length -Wpointer-arith -
Wmissing-prototypes -Wstrict-prototypes -Wreturn-type -Wswitch -Wshadow 
-Wcast-qual -Wwrite-strings -Wno-sign-compare -fno-zer
o-initialized-in-bss -Di386 -I. -I/usr/src/sys/contrib/dev/ath/netbsd 
-I/usr/src/sys/arch -I/usr/src/sys -nostdinc -DLKM -DMAX
USERS=32 -D_KERNEL -D_KERNEL_OPT 
-I/usr/src/sys/lib/libkern/../../../common/lib/libc/quad 
-I/usr/src/sys/lib/libkern/../../../
common/lib/libc/string 
-I/usr/src/sys/lib/libkern/../../../common/lib/libc/arch/i386/string 
-I/usr/src/sys/dist/ipf -c /usr/sr
c/sys/dev/ic/aac.c
cc1: warnings being treated as errors
/usr/src/sys/dev/ic/aac.c: In function 'aac_attach':
/usr/src/sys/dev/ic/aac.c:208: warning: dereferencing type-punned pointer will 
break strict-aliasing rules
/usr/src/sys/dev/ic/aac.c: In function 'aac_describe_controller':
/usr/src/sys/dev/ic/aac.c:379: warning: pointer targets in passing argument 3 
of 'bitmask_snprintf' differ in signedness
/usr/src/sys/dev/ic/aac.c: In function 'aac_init':
/usr/src/sys/dev/ic/aac.c:475: warning: dereferencing type-punned pointer will 
break strict-aliasing rules

*** Failed target:  aac.o

Can someone enlighten me as to what I have forgotten to do....

TIA,
Dave

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