7.0 upgrade compile error

[Casey Scott]

I am trying to upgrade from 6.3 to 7.0. With latest source, buildworld dies
with:

...
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c: In function 'uw_install_context_1':
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c:1472: warning: incompatible implicit declaration of built-in function 'abort'
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c:1480: warning: incompatible implicit declaration of built-in function 'memcpy'
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c:1486: warning: incompatible implicit declaration of built-in function 'memcpy'
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c:1490: warning: incompatible implicit declaration of built-in function 'memcpy'
In file included from /usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind-dw2.c:1518:
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc: In function '_Unwind_RaiseException_Phase2':
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc:75: warning: incompatible implicit declaration of built-in function 'abort'
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc: In function '_Unwind_Resume':
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc:238: warning: incompatible implicit declaration of built-in function 'abort'
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc: In function '_Unwind_Resume_or_Rethrow':
/usr/src/gnu/lib/libgcc/../../../contrib/gcc/unwind.inc:263: warning: incompatible implicit declaration of built-in function 'abort'
*** Error code 1

Stop in /usr/src/gnu/lib/libgcc.
*** Error code 1

I am not sure what to do about this! Any suggestions?

TIA,
Casey