Added a section in README to give details about use of
-DBUILD_SHARED_LIBS cmake option and existing documentation reformatted
to accommodate this.

Signed-off-by: Deepak Kumar Mishra <deepakkumar.mishra@arm.com>
Cc: Qais Yousef <qais.yousef@arm.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>