Fix hardcoded /tmp paths in testing (bug 13888)

[Joseph Myers]

On Tue, 26 Jun 2018, Florian Weimer wrote:

> * Joseph Myers:
> 
> > +CFLAGS-bug3.c += -DOBJPFX=\"$(objpfx)\"
> > +CFLAGS-bug4.c += -DOBJPFX=\"$(objpfx)\"
> > +CFLAGS-bug5.c += -DOBJPFX=\"$(objpfx)\"
> > +CFLAGS-test-fseek.c += -DOBJPFX=\"$(objpfx)\"
> > +CFLAGS-test-popen.c += -DOBJPFX=\"$(objpfx)\"
> > +CFLAGS-test_rdwr.c += -DOBJPFX=\"$(objpfx)\"
> 
> There is some overlap here with DJ's test-in-container patch, which
> also needs to find a test directory (although there it is
> $(common-objpfx)).
> 
> Should we make this available in a more general way, perhaps as a
> subdir-specific header file, or by changing the make rule for
> compiling tests?

Only a few tests need this at all.  (Even those tests may not strictly 
need it, in that other temporary file machinery could be used, but putting 
those files in objpfx was certainly the minimum incremental fix to the 
issue with those tests.)

-- 
Joseph S. Myers
joseph@codesourcery.com