data/dconf: Don't run "dconf update" if $(DESTDIR) is set

data/dconf: Don't run "dconf update" if $(DESTDIR) is set

dconf changed as of
https://git.gnome.org/browse/dconf/commit/?id=c211fc46496597c7ddabd73d623bae4037754916
to actually emit an error if /etc/dconf/db is empty.  When building
ibus in a system such as dpkg/rpm or gnome-continuous, there may
actually be nothing in that directory in the buildroot.

This will now cause "dconf update" as executed by this Makefile to
fail.  The fix is to just check $(DESTDIR), like we should do for all
triggers (e.g. gtk-update-icon-cache too).  It's never useful to
execute these from per-component Makefiles if $(DESTDIR) is set.

Instead, these meta-build systems (dpkg/rpm/jhbuild/Continuous) all
take care of execution of triggers on their own.

[Peng, 2014-01-15 13:04:48]

https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am
File data/dconf/Makefile.am (right):

https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am#newcode64
data/dconf/Makefile.am:64: if test -z "$(DESTDIR)"; then \
What about if the db exists in destdir?
Maybe you could consider adding a configure option for it, or cheching db in
destdir before calling dconf update.

[cgwalters, 2014-01-15 14:13:56]

On 2014/01/15 13:04:48, Peng wrote:
> https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am
> File data/dconf/Makefile.am (right):
> 
>
https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am#newcode64
> data/dconf/Makefile.am:64: if test -z "$(DESTDIR)"; then \
> What about if the db exists in destdir?

No one does that.  DESTDIR is for package systems to gather the files
for an individual component.  This patch works exactly how
many other real-world Makefiles do. 

For example:
https://git.gnome.org/browse/librsvg/tree/gdk-pixbuf-loader/Makefile.am#n52

[Peng, 2014-01-16 02:26:38]

On 2014/01/15 14:13:56, cgwalters wrote:
> On 2014/01/15 13:04:48, Peng wrote:
> > https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am
> > File data/dconf/Makefile.am (right):
> > 
> >
>
https://codereview.appspot.com/51730044/diff/1/data/dconf/Makefile.am#newcode64
> > data/dconf/Makefile.am:64: if test -z "$(DESTDIR)"; then \
> > What about if the db exists in destdir?
> 
> No one does that.  DESTDIR is for package systems to gather the files
> for an individual component.  This patch works exactly how
> many other real-world Makefiles do. 
> 
> For example:
> https://git.gnome.org/browse/librsvg/tree/gdk-pixbuf-loader/Makefile.am#n52

I see. lgtm.