The build system for plextor-tool seems to aim at an old version of gnome using gnome-config: x86_64-pc-linux-gnu-gcc -march=amdfam10 -O2 -ggdb -pipe -Wall `gnome-config --cflags applets` -Icommon/ -DUSE_GNOME -c -o gnome/session.o gnome/session.c /bin/sh: gnome-config: command not found gnome/session.c:34:19: error: gnome.h: No such file or directory gnome/session.c:36:27: error: applet-widget.h: No such file or directory I suggest you disable the gnome USE flag for that ebuild unless someone can offer a fix for this issue.
gnome-panel is dead -> please disable that support completely
Fixed in portage. + 27 Aug 2013; Samuli Suominen <ssuominen@gentoo.org> + files/plextor-tool-0.5.0-build.patch, plextor-tool-0.5.0.ebuild: + Stop building the gnome-panel 2.x applet (and modify the -build.patch to not + call gnome-config) wrt #345449 by Martin von Gagern