Add basic Android platform module
Create a Platform/Android module that includes Platform/Linux since Android is based on Linux. Provide only the minimal settings needed to get builds with Android NDK toolchains to work. Disable use of RPATH since the Android loader ignores it and we cannot predict the install destination anyway. Android supports soname but shared library names must end in ".so" and we cannot represent the versioned names with associated symlinks on all host operating systems anyway. However, we do want the SONAME of library files to be set so that linking to them by path to the library file produces NEEDED entries with the soname and not the path. Add a new CMAKE_PLATFORM_NO_VERSIONED_SONAME setting to tell the cmTarget::GetLibraryNames method that not to use the VERSION or SOVERSION target properties in the soname.