Put stripped debug symbols back into bluecherry-dbg

Previously, the debug symbols were discarded by our building
environment.

With this change, bluecherry-dbg packages again contain the debug
symbols stripped from the built code.

Alternatively, we could change this code to "dh_strip --keep-debug"
which adds 7 MB to bluecherry.deb, taking it from 28M to 35M.

The situation with instant access to crash backtraces enriched with
debug symbols is now the following: the stack trace logged by bc-server
itself lists the libraries for every stack frame, but not function names
or line nubmers. This info is in the debug info shipped, but it is not
used by glibc's backtrace() (wouldn't even if we avoid stripping
overall).

The ways to use all the debug info are:

sudo -u bluecherry gdb -ex run -ex bt --args /usr/sbin/bc-server -s

sudo -u bluecherry rr record /usr/sbin/bc-server -s
sudo -u bluecherry rr replay # there: continue, bt...

debian/rules

@@ -13,14 +13,8 @@ RELEASE_NAME := $(shell ./scripts/build_helper/get_distro_release_name.sh)
 
 .PHONY: override_dh_strip debian/control
 
-# Don't build debug packages anymore
-
-#override_dh_strip:
-#	dh_strip --dbg-package=bluecherry-dbg
-
-#override_dh_installinit: sbin-start=$(wildcard /sbin/start)
-#override_dh_installinit:
-#	dh_installinit $(if $(sbin-start),--name=bluecherry)
+override_dh_strip:
+	dh_strip --dbg-package=bluecherry-dbg
 
 # Add support for systemd