A while ago I learned from Nicola that GNUstep make provides the
xxx_COPY_INTO_DIR variable to suppress the standard installation
of a tool and install it into another application. Unfortunately,
PC does not yet support this variable. Until PC supports adding
arbitrary variables to either GNUmake or GNUmakefile.preamble,
the best solution I see for adding support for xxx_COPY_INTO_DIR
is (ab)using the installation directory project attribute. The
attached patch checks the INSTALLDIR project attribute for an
application or tool project and sets xxx_COPY_INTO_DIR in the
generated makefile when the attribute is a relative path, not
one of the standard installation domains SYSTEM, LOCAL, NETWORK,
and USER, and it does not start with a $. The latter is just to
prevent the code from getting confused by the default value for
the installation directory, which is currently $(HOME)/GNUstep
for an application and $(HOME)/GNUstep/Tools for a tool project.
These paths and other absolute paths continue to be handled by
passing DESTDIR to the make command. I'm aware that this is more
a hack, but it serves its purpose well for me and I guess it may
be useful for others, too.