BUILD_SHARED_LIBS is a global flag so we don't need to set a default
option for it in both libhsakmt and hsa-runtime, only the top level
CMakeLists file. Also updated README to reflect that libhsakmt is
always built statically and gets linked to libhsa-runtime.
Change-Id: I1511f68a268032bec9758bc731d8074f33ec980f
Create a new top-level CMakeLists.txt file to control building thunk
and ROCr. kfdtest and rocrtest are built separately.
Most of the cmake code that existed for thunk, ROCr, rocrtst and kfdtest
still reside in their respective CMakeLists.txt files, except the
CPack packaging directives which have been moved to the top-level
CMakeLists.txt.
Change-Id: I1a537359029504af8b1abb324bc6f0d75d98471e