Unable to build GDB 13.1 on Solaris 11.3 Sparc

I am trying (and failing) to build GDB 13.1 on Solaris 11.3 Sparc.

Here is my configuration script.

CXXFLAGS='-g3 -O0' \
CFLAGS='-g3 -O0' \
NM=/usr/bin/gnm \
SHELL=/usr/bin/bash \
AR=/usr/bin/gar \
AS=/usr/bin/as \
CC=/home/build/gcc/git/bin/gcc \
CXX=/home/build/gcc/git/bin/g++ \
../configure \
--with-mpc=/usr/local \
--with-gmp=/usr/local \
--with-mpfr=/usr/local \
--enable-64-bit-bfd \
--enable-tui \
--with-curses \
--disable-bootstrap \
--disable-binutils \
--disable-ld \
--disable-gprof \
--disable-gprofng \
--disable-gold \
--disable-gas \
--disable-sim

(Some flags taken from https://sourceware.org/gdb/wiki/BuildingNatively .)

The makefile creates ./gdb inside the build directory and then stops as 
follows:

checking for libgmp... no
configure: error: GMP is missing or unusable
gmake[1]: *** [Makefile:11447: configure-gdb] Error 1
gmake[1]: Leaving directory '/home/build/opt/gdb-13.1/bld'

I have libgmp (and building gcc 13 uses it) in /usr/local/lib:

/usr/local/lib/libgmp.a:        current ar archive, 32-bit symbol table
/usr/local/lib/libgmp.la:       commands text
/usr/local/lib/libgmp.so:       ELF 64-bit MSB dynamic lib SPARCV9 
Version 1, UltraSPARC3 Extensions Required, dynamically linked, not 
stripped, no debugging information available
/usr/local/lib/libgmp.so.10:    ELF 64-bit MSB dynamic lib SPARCV9 
Version 1, UltraSPARC3 Extensions Required, dynamically linked, not 
stripped, no debugging information available
/usr/local/lib/libgmp.so.10.4.1:        ELF 64-bit MSB dynamic lib 
SPARCV9 Version 1, UltraSPARC3 Extensions Required, dynamically linked, 
not stripped, no debugging information available

Now I note that the Makefile is compiling to 32-bit objects but I have a 
32-bit libgmp.a.  (I tried adding "-m64" but that caused other problems.)

I am stumped.  How do I proceed?

N.