bug#13002: directory variables in VALAFLAGS are expanded after cd

[Daiki Ueno]

Hi,

I see quite a few Vala projects setting VALAFLAGS as follows:

libfolks_eds_la_VALAFLAGS = \
        --vapidir=. \
        --vapidir=$(top_srcdir)/folks \
        ...

This is referred by the generated rule in Makefile.in as:

$(AM_V_VALAC)$(am__cd) $(srcdir) && $(VALAC) $(libfolks_eds_la_VALAFLAGS) 
$(VALAFLAGS) -C $(libfolks_eds_la_SOURCES)

Here, if $(srcdir) != $(builddir) and $(top_srcdir) is a relative path
from $(builddir), the --vapidir option will point to a wrong location.

Though this could be worked around by using $(abs_top_srcdir) instead of
$(top_srcdir), it looks to me a bit unintuitive.  It would be nice that
automake handles this case nicely.

Regards,
-- 
Daiki Ueno