Please describe the problem:
glib-2.18.3/docs/reference/glib/Makefile.in contains this code

          ! which gtkdoc-rebase >/dev/null 2>&1 || \
            gtkdoc-rebase --relative --dest-dir=$(DESTDIR) --html-dir=$${installdir} ; \

If gtkdoc-rebase is missing, this breaks on Solaris, as /usr/bin/which does not set an exit code, if the requested program cannot be found.

Steps to reproduce:
1. 
2. 
3. 


Actual results:
"make install" exits with an error, leaving behind a half installed package

Expected results:
"make install" succeeds

Does this happen every time?
yes

Other information:
The corresponding code in glib 2.18.0 did work:

          which gtkdoc-rebase >/dev/null && \
            gtkdoc-rebase --relative --dest-dir=$(DESTDIR) --html-dir=$(DESTDIR)$(TARGET_DIR) ; \