Bug#1067577: sysprof: B-D on libunwind-dev which is not generally available

[Thorsten Glaser]

Source: sysprof
Version: 46~rc-1
Severity: important
Justification: unbuildable on some d-ports architectures
X-Debbugs-Cc: tg at mirbsd.de

libunwind-dev is not available for at least alpha, hurd-any,
loong64, m68k, sparc64, x32.

sysprof is a not unimportant part in the GNOME dependency chain
(IIRC seeing it for weston) and part of the t64 transition, so
having it generally available (with missed features if needed)
is needed.