Added gentoo compiling guide from Denis Dupeyron

Documentation/compiling/linux-gentoo.txt

+Compiling KiCad on Gentoo
+=========================
+
+Information
+-----------
+First written: 02-Mar-2010
+
+Written by: denis[dot]dupeyron[at]gmail[dot]com
+
+
+For regular users
+-----------------
+
+In order to install Kicad from sources in Gentoo you just need to:
+----
+    # emerge kicad
+----
+The package manager will resolve all dependencies, download the
+necessary source code, and then configure it, compile it and install
+it. You're done.
+
+If you want to fine-tune your installation you can set some of the USE
+flags. Do the following to see them:
+----
+    # emerge -vp kicad
+----
+The currently available USE flags are:
+debug: make a debug build
+doc: install documentation
+examples: install examples
+python: enable python
+minimal: do not install the default component libraries (unsupported)
+
+Enable or disable whatever USE flag(s) you want or don't want, for
+example like this:
+----
+    # echo "sci-electronics/kicad doc -python" >> /etc/portage/package.use
+----
+Here we've just enabled documentation and disabled python. After that
+you can emerge kicad.
+
+
+For advanced users
+------------------
+If you're running stable gentoo and want the unstable (more recent)
+version of kicad then do the following before running emerge:
+----
+    # echo "sci-electronics/kicad ~arch" >> /usr/portage/package.keywords
+----
+where ~arch is either ~amd64, ~ppc, ~ppc64 or ~x86 depending on your
+architecture.
+
+If you want to experiment with cmake flags to pass for compilation or
+override one that's set by default in the ebuild you can do so like
+this:
+----
+    # MYCMAKEARGS="-DUSE_WX_GRAPHICS_CONTEXT=ON" emerge kicad
+----
+
+
+For Kicad developers and packagers
+----------------------------------
+
+You can install from live sources instead of the latest package
+version by doing the following:
+----
+    # echo "sci-electronics/kicad **" >> /etc/portage/package.keywords
+    # emerge kicad
+----
+The version of Kicad that is going to be installed is called
+kicad-99999999. The package manager will then checkout all sources
+from the subversion repository, or update it to the latest revision if
+you had already installed the live version of Kicad, and then do its
+usual thing. You will get an additional USE flag called dev-doc which
+is to set if you want to build the Doxygen documentation.
+
+If you want to build a specific revision of Kicad from the subversion
+repository, you can do:
+----
+    # ESVN_REVISION="2400" emerge kicad
+----
+Note that you can combine that with MYCMAKEARGS on the same command-line.
+
+If you have built and tested Kicad and want to package it, it's very simple:
+----
+    # quickpkg kicad
+----
+This works for both live and standard installs of Kicad. The tarball
+will be in /usr/portage/packages.
+
+Here is one way to find out which packages contain the shared
+libraries Kicad was built against, and what exact version they are:
+----
+    # equery belongs $(cat /var/db/pkg/sci-electronics/kicad-99999999/NEEDED | cut -d ' ' -f 2 | tr ',' '\n' | sort -u) | sort -u
+----
+You should replace kicad-99999999 with the version you have just
+built. You might want to be careful with the interpretation of the
+results from the above one-liner, but if you made it this far you
+obviously know what you're dealing with.