Add build-id links to rpm for all ELF files.

Add build-id links to rpm for all ELF files.

This patch moves the main ELF file build-id symlinks from the
debuginfo package into the main package. And uses different
base directories for the main ELF file build-id symlink.
For the main build-id use /usr/lib/.build-id and for the debug
build-id use /usr/lib/debug/.build-id.

There are two reasons for doing this. The main package and the
debuginfo package might get out of sync, or the debuginfo package
might not be installed at all. In which case finding the main ELF
file through the build-id symlink becomes impossible. Secondly by
moving the main ELF build-id symlink in its own directory the
/usr/lib/debug directory gets populated with only debuginfo files
which is convenient if the user might want to have that directory
populated through a network mountpoint.

To support the new logic the symlink code has been moved from
find-debuginfo.sh to build/files.c.

This also includes support for a new config %_build_id_links that
defaults to compat. The other settings are none, alldebug (the old
style) and separate. compat is like separate, but adds a compatibility
link under /usr/lib/debug/.build-id for the main build-id symlink.

There are several new testcases added to test the various settings
using the new keyword "buildid".

Signed-off-by: Mark Wielaard <mjw@redhat.com>