This is a regression from 4.1.3 which configures without these errors (although it doesn't seem to pay any attention to the fact that it's a 32-bit build and uses a 64-bit compiler).
$ nice gmake BUILDTYPE=12d BUILDDIR=/build/sebor/stdcxx-gcc-3.2.1-12d/
GNUmakefile:309: "CONFIG not specified, using gcc.config"
creating BUILDDIR=/build/sebor/stdcxx-gcc-3.2.1-12d/
generating /build/sebor/stdcxx-gcc-3.2.1-12d//makefile.in from /tmp_mnt/amd/devco/sebor/stdcxx/etc/config/gcc.config
gmake[1]: Entering directory `/build/sebor/stdcxx-gcc-3.2.1-12d'
gmake[2]: Entering directory `/build/sebor/stdcxx-gcc-3.2.1-12d/include'
gmake config
gmake[3]: Entering directory `/build/sebor/stdcxx-gcc-3.2.1-12d/include'
configuring stdcxx 4.2.0 for gcc-3.2.1 on hp-ux-b.11.11-9000-800
checking if the compiler is sane no
int main () { return 0; }
gcc -pthread -I. -pedantic -nostdinc++ -O2 -m32 -W -Wall -Wcast-qual -Winline -Wshadow -Wwrite-strings -Wno-long-long -Wcast-align -c a.cpp -o a.o
gcc: unrecognized option `-pthread'
cc1plus: invalid option `32'
gmake[3]: *** [sane] Error 1
gmake[3]: Leaving directory `/build/sebor/stdcxx-gcc-3.2.1-12d/include'
gmake[2]: *** [config.h] Error 2
gmake[2]: Leaving directory `/build/sebor/stdcxx-gcc-3.2.1-12d/include'
gmake[1]: *** [config] Error 2
gmake[1]: Leaving directory `/build/sebor/stdcxx-gcc-3.2.1-12d'
gmake: *** [libstd] Error 2