This is a packager/packaging problem, not an rpm problem. Basically,
you need to "look before you leap" if you're using rpm to build
packages.

Alternatively, you might try these macros that will install all
components from a src.rpm in the same /J/name-version-release
directory (built binaries and src.rpm end up there too):

%_topdir        /J
%_ntopdir       %{_topdir}/%{name}-%{version}-%{release}
%_builddir      %{_ntopdir}
%_rpmdir        %{_ntopdir}
%_sourcedir     %{_ntopdir}
%_specdir       %{_ntopdir}
%_srpmdir       %{_ntopdir}
%_rpmfilename   %%{NAME}-%%{VERSION}-%%{RELEASE}.%%{ARCH}.rpm