[PATCH]: minor Makefile.in tweak

[Tom Tromey]

Michael> Sun's 'make' on Solaris-x86 seems to work better if this
Michael> dependency is made explicitly relative to $(srcdir).  I don't
Michael> know if that is a bug in VPATH handling, or what...

FYI, generally speaking vendor makes do not implement VPATH correctly.
For automake we decided to only support this feature with GNU make.

Some makes are almost good enough to use, if you add tweaks of one
sort or another.  Sun's make is one of these, but I forget what tweaks
are required.

Anyway, I don't think gdb is required (i.e., per GNU coding standards)
to support VPATH for non-GNU makes.  In case you care.

Tom