For the moment, you have to ./configure with --prefix=same prefix as you configured
epiphany with.

Please see the README files in each extension subdirectory for more specific
information.

How to choose which extensions to build:

./configure --with-extensions=ext1,ext2,...

where ext1, ext2 ... are one of the following:

error-viewer		Error viewer extension [i.e., Javascript, HTML errors]
gestures		Gestures extension
popup-blocker		Popup blocker extension
tabsmenu		Tabs Menu extension
all			All of the above extensions
sample			Sample extension [use this as a template]
sample-mozilla		Sample extension which uses mozilla api [use as a template]
