I fixed the following with: (On Ubuntu)
sudo apt-get install gcc-multilib
paul@jacko:~/gpc1-build$ LANG=C make
make[1]: Entering directory '/home/paul/gpc1-build/libiberty'
make[2]: Entering directory '/home/paul/gpc1-build/libiberty/testsuite'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/paul/gpc1-build/libiberty/testsuite'
make[1]: Leaving directory '/home/paul/gpc1-build/libiberty'
make[1]: Entering directory '/home/paul/gpc1-build/intl'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/home/paul/gpc1-build/intl'
make[1]: Entering directory '/home/paul/gpc1-build/gcc'
cd ../../gpc1/gcc-3.4.6/gcc/p/rts && make -f Makefile.in srcdir=. GCC_VERSION="3.4.6" SHELL="/bin/sh" CFLAGS="-g -O2" PFLAGS="" AR_FLAGS="rc" RTSFLAGS="" GPC_DESTDIR="../.." AR="ar" RANLIB="ranlib" RANLIB_TEST="" generated-files
make[2]: Entering directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[2]: Nothing to be done for 'generated-files'.
make[2]: Leaving directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
cd ../../gpc1/gcc-3.4.6/gcc/p/rts && make -f Makefile.in srcdir=. GCC_VERSION="3.4.6" SHELL="/bin/sh" CFLAGS="-g -O2" PFLAGS="" AR_FLAGS="rc" RTSFLAGS="" GPC_DESTDIR="../.." AR="ar" RANLIB="ranlib" RANLIB_TEST="" generated-files
make[2]: Entering directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[2]: Nothing to be done for 'generated-files'.
make[2]: Leaving directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
cd ../../gpc1/gcc-3.4.6/gcc/p/rts && make -f Makefile.in srcdir=. GCC_VERSION="3.4.6" SHELL="/bin/sh" CFLAGS="-g -O2" PFLAGS="" AR_FLAGS="rc" RTSFLAGS="" GPC_DESTDIR="../.." AR="ar" RANLIB="ranlib" RANLIB_TEST="" generated-files
make[2]: Entering directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[2]: Nothing to be done for 'generated-files'.
make[2]: Leaving directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
cd ../../gpc1/gcc-3.4.6/gcc/p/rts && make -f Makefile.in srcdir=. GCC_VERSION="3.4.6" SHELL="/bin/sh" CFLAGS="-g -O2" PFLAGS="" AR_FLAGS="rc" RTSFLAGS="" GPC_DESTDIR="../.." AR="ar" RANLIB="ranlib" RANLIB_TEST="" generated-files
make[2]: Entering directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[2]: Nothing to be done for 'generated-files'.
make[2]: Leaving directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
cd ../../gpc1/gcc-3.4.6/gcc/p/rts && make -f Makefile.in srcdir=. GCC_VERSION="3.4.6" SHELL="/bin/sh" CFLAGS="-g -O2" PFLAGS="" AR_FLAGS="rc" RTSFLAGS="" GPC_DESTDIR="../.." AR="ar" RANLIB="ranlib" RANLIB_TEST="" generated-files
make[2]: Entering directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[2]: Nothing to be done for 'generated-files'.
make[2]: Leaving directory '/home/paul/gpc1/gcc-3.4.6/gcc/p/rts'
make[1]: Circular libgcc.a <- pascal dependency dropped.
/home/paul/gpc1-build/gcc/xgcc -B/home/paul/gpc1-build/gcc/ -B/usr/local/x86_64-unknown-linux-gnu/bin/ -B/usr/local/x86_64-unknown-linux-gnu/lib/ -isystem /usr/local/x86_64-unknown-linux-gnu/include -isystem /usr/local/x86_64-unknown-linux-gnu/sys-include -O2 -DIN_GCC -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -isystem ./include -I. -I. -I../../gpc1/gcc-3.4.6/gcc -I../../gpc1/gcc-3.4.6/gcc/. -I../../gpc1/gcc-3.4.6/gcc/../include -g0 -finhibit-size-directive -fno-inline-functions -fno-exceptions -fno-zero-initialized-in-bss -fno-unit-at-a-time -fno-omit-frame-pointer -fno-asynchronous-unwind-tables \
-c ../../gpc1/gcc-3.4.6/gcc/crtstuff.c -DCRT_BEGIN \
-o crtbegin.o
In file included from /usr/include/bits/errno.h:26,
from /usr/include/errno.h:28,
from ../../gpc1/gcc-3.4.6/gcc/tsystem.h:85,
from ../../gpc1/gcc-3.4.6/gcc/crtstuff.c:62:
/usr/include/linux/errno.h:1:23: asm/errno.h: No such file or directory
make[1]: *** [Makefile:1273: crtbegin.o] Error 1
make[1]: Leaving directory '/home/paul/gpc1-build/gcc'
make: *** [Makefile:23375: all-gcc] Error 2
paul@jacko:~/gpc1-build$ LANG=C make