how to build/install mesa w/ the right --prefix for ubuntu 14.04 x86_64

Hi,

What should I set --prefix to for ubuntu 14.04 so that 'make install' 
installs the .so files to the right places on ubuntu 14.04 x86_64?

Here's why I'm confused about something that is probably simple :)

http://www.mesa3d.org/autoconf.html says the default install location is 
/usr/local. However, Its seems ubuntu by default has the gfx .so files 
located in
	/usr/lib/x86_64-linux-gnu
	/usr/lib/x86_64-linux-gnu/mesa
	/usr/lib/x86_64-linux-gnu/mesa-egl
	/usr/lib/x86_64-linux-gnu/dri

And, when I build w/ '--prefix=/home/my-prefix/install', the .so files are @
	/home/my-prefix/install/lib
	/home/my-prefix/install/lib/dri

I guess I could try to not set --prefix or set 
'--prefix=/usr/lib/x86_64' and see what happens but I am not confident 
the .so files will be installed to a place. The reason I haven't just 
flat out tried this yet is b/c I don't want to hose my machine :)


#
# My build steps
#
./autogen.sh --prefix=/home/my-prefix/install --enable-gles1 
--enable-gles2 --enable-openvg --enable-osmesa --enable-xa --enable-gbm 
--enable-gallium-egl --enable-gallium-gbm --enable-glx-tls 
--with-egl-platforms="drm,x11" --with-gallium-drivers="i915,swrast,svga"

make

make install



Thanks for any guidance you can provide,
-Mike