* install extensions: gtk2-dev openssl-1.1.1-dev compiletc squashfs-tools
  (can't get the configure script to find gtkspell, so I just dropped that one)
* export CFLAGS="-mtune=generic -Os -pipe"
  export CXXFLAGS="-mtune=generic -Os -pipe"
  export LDFLAGS="-Wl,-O1"
* export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
* ./configure --prefix=/usr/local
* make
* touch /tmp/mark
* make DESTDIR=/tmp/sylpheed install

...
libtool: install: /usr/bin/install -c .libs/libsylpheed-plugin-0.so.1.3.0T /tmp/sylpheed/usr/local/lib/libsylpheed-plugin-0.so.1.3.0
libtool: install: (cd /tmp/sylpheed/usr/local/lib && { ln -s -f libsylpheed-plugin-0.so.1.3.0 libsylpheed-plugin-0.so.1 || { rm -f libsylpheed-plugin-0.so.1 && ln -s libsylpheed-plugin-0.so.1.3.0 libsylpheed-plugin-0.so.1; }; })
libtool: install: (cd /tmp/sylpheed/usr/local/lib && { ln -s -f libsylpheed-plugin-0.so.1.3.0 libsylpheed-plugin-0.so || { rm -f libsylpheed-plugin-0.so && ln -s libsylpheed-plugin-0.so.1.3.0 libsylpheed-plugin-0.so; }; })
libtool: install: /usr/bin/install -c .libs/libsylpheed-plugin-0.lai /tmp/sylpheed/usr/local/lib/libsylpheed-plugin-0.la
install: can't stat '.libs/libsylpheed-plugin-0.lai': No such file or directory
make[3]: *** [Makefile:700: install-libLTLIBRARIES] Error 1
make[3]: Leaving directory '/mnt/sda2/tce/src/sylpheed-3.7.0/src'
make[2]: *** [Makefile:1118: install-am] Error 2
make[2]: Leaving directory '/mnt/sda2/tce/src/sylpheed-3.7.0/src'
make[1]: *** [Makefile:953: install-recursive] Error 1
make[1]: Leaving directory '/mnt/sda2/tce/src/sylpheed-3.7.0/src'
make: *** [Makefile:1112: install] Error 2

* Desperation after lots of messing about:
 # touch src/.libs/libsylpheed-plugin-0.lai

* make DESTDIR=/tmp/sylpheed install

Works!

* it's something to do with libtool. Not sure why that's not working, but libtool not being installed might be a start...

* tce-load -wil libtool
* make clean
* make

* It can't find "/usr/local/lib/libglib-2.0.la", and indeed it's not there. But glib2-dev.tcz is loaded, and tce-ab shows that no packages provide libglib-2.0.la, so it's not happening. I'll see if I can get by with just an empty file there...
 # sudo touch /usr/local/lib/libglib-2.0.la
  - I don't think this did work, and I had to copy a libglib-2.0.la file found online. Unfortunately it was late
    and I obviously forgot to document this. I don't remember where I found it and didn't keep a copy. Will just
    have to figure this bit out from scratch next time...

* split /tmp/sylpheed into   sylpheed-dev sylpheed-doc sylpheed-locale
* In each dir. run "find usr -not -type d > ../program_name.tcz.list".
* Make into extensions using mksquashfs. "mksquashfs sylpheed sylpheed.tcz
* "md5sum sylpheed.tcz > sylpheed.tcz.md5.txt" etc...
* Create dep file.
* Copy sylpheed.tcz (+ dep, md5) to "tce/optional" and reboot.

* tce-load -i sylpheed
* sylpheed &

Works!

* Tested after deleting all links in /usr/local, added font, curl, and iconv dependencies.