Ok. Beginning with tip
hg update -r a00379f6f8c4
then bootstrap, configure, make. Which completed without error. Finally ...
/bin/sh config.status oct-conf-post.h-tmp oct-conf-post.h
config.status: creating oct-conf-post.h-tmp
config.status: executing oct-conf-post.h commands
/bin/sh ./build-aux/mk-octave-config-h.sh config.h > octave-config.h-t && \
if [ -s octave-config.h-t ]; then /bin/sh ./build-aux/move-if-change octave-config.h-t octave-config.h; else echo "octave-config.h-t is empty!" 1>&2; rm -f octave-config.h-t; exit 1; fi
rm -f libinterp/builtin-defun-decls.h-t && \
if [ -s libinterp/builtin-defun-decls.h-t ]; then /bin/sh ./build-aux/move-if-change libinterp/builtin-defun-decls.h-t libinterp/builtin-defun-decls.h; else echo "libinterp/builtin-defun-decls.h-t is empty!" 1>&2; rm -f libinterp/builtin-defun-decls.h-t; exit 1; fi
/bin/sh config.status liboctave/mk-version-h.sh-tmp liboctave/mk-version-h.sh
config.status: creating liboctave/mk-version-h.sh-tmp
config.status: executing liboctave/mk-version-h.sh commands
/bin/sh config.status libinterp/corefcn/mk-mxarray-h.sh-tmp libinterp/corefcn/mk-mxarray-h.sh
config.status: creating libinterp/corefcn/mk-mxarray-h.sh-tmp
config.status: executing libinterp/corefcn/mk-mxarray-h.sh commands
/bin/sh config.status liboctave/external/mk-f77-def.sh-tmp liboctave/external/mk-f77-def.sh
config.status: creating liboctave/external/mk-f77-def.sh-tmp
config.status: executing liboctave/external/mk-f77-def.sh commands
/bin/sh ./libtool --tag=CXX --mode=link g++ -std=gnu++11 -fPIC -D_THREAD_SAFE -pthread -Wall -W -Wshadow -Wold-style-cast -Wformat -Wpointer-arith -Wwrite-strings -Wcast-align -Wcast-qual -g -O2 -version-info 4:0:0 -no-undefined -bindir /usr/local/bpabbott/octave/bin -F/usr/local/Cellar/qt/5.10.1/lib -L/usr/local/opt/hdf5/lib -L/usr/local/Cellar/graphicsmagick/1.3.29/lib -L/usr/local/Cellar/fftw/3.3.7_1/lib -L/usr/local/Cellar/fftw/3.3.7_1/lib -L/usr/local/Cellar/arpack/3.5.0/libexec/lib -L/usr/local/Cellar/fftw/3.3.7_1/lib -L/usr/local/Cellar/fftw/3.3.7_1/lib -L/usr/local/Cellar/pcre/8.42/lib -L/usr/local/opt/readline/lib -L/usr/local/opt/sqlite/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/bison/lib -L/usr/local/opt/gettext/lib -L/usr/local/opt/libffi/lib -L/usr/local/opt/icu4c/lib -L/usr/local/opt/texinfo/lib -L/usr/local/opt/qt/lib -o libgui/liboctgui.la -rpath /usr/local/bpabbott/octave/lib/octave/5.0.0 libgui/liboctgui_la-liboctgui-build-info.lo libgui/qterminal/libqterminal.la libgui/src/libgui-src.la libgui/graphics/libgui-graphics.la libinterp/liboctinterp.la liboctave/liboctave.la -framework QtNetwork -framework QtOpenGL -framework QtPrintSupport -framework QtHelp -framework QtWidgets -framework QtGui -framework QtSql -framework QtCore -lqscintilla2_qt5 -framework OpenGL -L/usr/local/opt/freetype/lib -lfreetype -lhdf5 -lGraphicsMagick++ -lGraphicsMagick -lz -lfftw3_threads -lfftw3 -lfftw3f_threads -lfftw3f -framework OpenGL -lfontconfig -lfreetype -framework Carbon -lgl2ps -lcurl -lcholmod -lumfpack -lamd -lcamd -lcolamd -lccolamd -lcxsparse -lsuitesparseconfig -larpack -lqrupdate -lfftw3_threads -lfftw3 -lfftw3f_threads -lfftw3f -L/usr/local/opt/veclibfort/lib -lvecLibFort -lreadline -lncurses -lpcre -ldl -L/usr/local/opt/readline/lib -L/usr/local/opt/sqlite/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/bison/lib -L/usr/local/opt/gettext/lib -L/usr/local/opt/libffi/lib -L/usr/local/opt/icu4c/lib -L/usr/local/opt/texinfo/lib -L/usr/local/opt/qt/lib -L/usr/local/Cellar/gcc/8.1.0/lib/gcc/8/gcc/x86_64-apple-darwin17.5.0/8.1.0 -L/usr/local/Cellar/gcc/8.1.0/lib/gcc/8/gcc/x86_64-apple-darwin17.5.0/8.1.0/../../.. -lgfortran -lquadmath -lm -lm -liconv -lm libtool: link: rm -fr libgui/.libs/liboctgui.4.dylib libgui/.libs/liboctgui.dylib libgui/.libs/liboctgui.la libgui/.libs/liboctgui.lai libtool: link: g++ -std=gnu++11 -dynamiclib -o libgui/.libs/liboctgui.4.dylib libgui/.libs/liboctgui_la-liboctgui-build-info.o -Wl,-force_load,libgui/qterminal/.libs/libqterminal.a -Wl,-force_load,libgui/src/.libs/libgui-src.a -Wl,-force_load,libgui/graphics/.libs/libgui-graphics.a -L/usr/local/opt/hdf5/lib -L/usr/local/Cellar/graphicsmagick/1.3.29/lib -L/usr/local/Cellar/fftw/3.3.7_1/lib -L/usr/local/Cellar/arpack/3.5.0/libexec/lib -L/usr/local/Cellar/pcre/8.42/lib -L/usr/local/opt/readline/lib -L/usr/local/opt/sqlite/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/bison/lib -L/usr/local/opt/gettext/lib -L/usr/local/opt/libffi/lib -L/usr/local/opt/icu4c/lib -L/usr/local/opt/texinfo/lib -L/usr/local/opt/qt/lib libinterp/.libs/liboctinterp.dylib -L/usr/local/opt/openblas/lib -L/usr/local/opt/veclibfort/lib -L/usr/local/Cellar/gcc/8.1.0/lib/gcc/8/gcc/x86_64-apple-darwin17.5.0/8.1.0 -L/usr/local/Cellar/gcc/8.1.0/lib/gcc/8/gcc/x86_64-apple-darwin17.5.0/8.1.0/../../.. -L/usr/local/opt/freetype/lib -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib /Users/bpabbott/Development/mercurial/default/sources/liboctave/.libs/liboctave.dylib liboctave/.libs/liboctave.dylib -framework QtNetwork -framework QtOpenGL -framework QtPrintSupport -framework QtHelp -framework QtWidgets -framework QtGui -framework QtSql -framework QtCore -lqscintilla2_qt5 -framework OpenGL -lhdf5 /usr/local/Cellar/graphicsmagick/1.3.29/lib/libGraphicsMagick++.dylib /usr/local/Cellar/graphicsmagick/1.3.29/lib/libGraphicsMagick.dylib -lbz2 -lltdl -lpthread -lz -lfontconfig -lfreetype -framework Carbon -lgl2ps -lcurl -lcholmod -lumfpack -lamd -lcamd -lcolamd -lccolamd -lcxsparse -lsuitesparseconfig /usr/local/Cellar/arpack/3.5.0/libexec/lib/libarpack.dylib -lopenblas -lqrupdate -lfftw3_threads -lfftw3 -lfftw3f_threads -lfftw3f -lvecLibFort -lreadline -lncurses -lpcre -ldl -lgfortran -lquadmath -liconv -lm -pthread -g -O2 -F/usr/local/Cellar/qt/5.10.1/lib -Wl,-dylib_file -Wl,/usr/local/bpabbott/octave/lib/octave/5.0.0/liboctave.6.dylib:/Users/bpabbott/Development/mercurial/default/sources/liboctave/.libs/liboctave.dylib -pthread -framework OpenGL -framework Carbon -framework QtNetwork -framework QtOpenGL -framework QtPrintSupport -framework QtHelp -framework QtWidgets -framework QtGui -framework QtSql -framework QtCore -install_name /usr/local/bpabbott/octave/lib/octave/5.0.0/liboctgui.4.dylib -compatibility_version 5 -current_version 5.0 -Wl,-single_module
libtool: link: (cd "libgui/.libs" && rm -f "liboctgui.dylib" && ln -s "liboctgui.4.dylib" "liboctgui.dylib")
Ben