--- gcc-4.1.0/gcc/Makefile.in.old
+++ gcc-4.1.0/gcc/Makefile.in
@@ -388,7 +388,10 @@
 CROSS_SYSTEM_HEADER_DIR = @CROSS_SYSTEM_HEADER_DIR@

 # autoconf sets SYSTEM_HEADER_DIR to one of the above.
-SYSTEM_HEADER_DIR = @SYSTEM_HEADER_DIR@
+# Purge it of unneccessary internal relative paths
+# to directories that might not exist yet.
+# The sed idiom for this is to repeat the search-and-replace until it doesn't match, using :a ... ta.
+SYSTEM_HEADER_DIR = `echo @SYSTEM_HEADER_DIR@ | sed -e :a -e "s,[^/]*/\.\.\/,," -e ta`

 # Control whether to run fixproto and fixincludes.
 STMP_FIXPROTO = @STMP_FIXPROTO@
@@ -3167,13 +3170,15 @@
 ../$(build_subdir)/fixincludes/fixincl: ; @ :

 # Build fixed copies of system files.
+# Abort if no system headers available, unless building a crosscompiler.
+# Canonicalize $gcc_tooldir/sys-include in same way as $SYSTEM_HEADER_DIR was canonicalized so test still works
 stmp-fixinc: gsyslimits.h macro_list \
   $(build_objdir)/fixincludes/fixincl \
   $(build_objdir)/fixincludes/fixinc.sh
        @if ! $(inhibit_libc) && test ! -d ${SYSTEM_HEADER_DIR}; then \
          echo The directory that should contain system headers does not exist: >&2 ; \
          echo "  ${SYSTEM_HEADER_DIR}" >&2 ; \
-         if test "x${SYSTEM_HEADER_DIR}" = "x${gcc_tooldir}/sys-include"; \
+         if test "x${SYSTEM_HEADER_DIR}" = "x`echo "${gcc_tooldir}/sys-include" | sed -e :a -e "s,[^/]*/\.\.\/,," -e ta`"; \
          then sleep 1; else exit 1; fi; \
        fi
        rm -rf include; mkdir include