RPM packager is broken

See gst-ci#21 (comment 147902)

Known problems are at least

1. broke due to changes in rpmbuild, which now enforce a strict directory hierarchy
2. debug symbols are missing
3. library symlinks (libfoo.so.1 -> libfoo.so.1.2.3) are broken (libfoo.so.1 -> packagename-version/libfoo.so.1.2.3) while the libraries are all in place (libfoo.so.1.2.3)

I don't know anything about RPM so maybe these are all actually caused by 1.

CC @ndufresne