-> install build dependencies:
$ tce-load -wi compiletc automake autogen-dev autoconf pkg-config gtk3-dev

-> per TC wiki, for maximum compatibility:
$ export CFLAGS="-mtune=generic -Os -pipe"
$ export CXXFLAGS="-mtune=generic -Os -pipe"
$ export LDFLAGS="-Wl,-O1"

-> finally:
$ cd gsimplecal-2.1
$ ./autogen.sh
$ ./configure --prefix=/usr/local
$ make
$ mkdir /opt/dest; sudo make DESTDIR=/opt/dest install