GNU make does not and has never supported a built-in variable $(PWD).

Of course, GNU make does now and has always (just like every other make) imported environment variables exported from the invoking process into GNU make variables, and some shells do set and maintain a $PWD environment variable.

So if your shell is one of those, then you would see a $(PWD) variable in make as well; but this is nothing GNU make is creating.  It's 100% dependent on the feature set of the shell invoking GNU make (never a good idea for a portable make environment!!)

If you use "make -p" so GNU make prints its database, it will tell you exactly where every variable defined came from.

Even simpler is to look at the NEWS file; all user-visible changes should be documented there:

Version 3.80
    ...

• A new built-in variable is defined, $(MAKEFILE_LIST). [...]

    ...

Version 3.77
    ...

• Make defines a new variable, "CURDIR", to contain the current working

  directory (after the -C option, if any, has been processed).
  Modifying this variable has no effect on the operation of make.

I tried to use ${CURDIR} and ${MAKEFILE_LIST} with a GNU make
on Solaris, but these variables are empty. In what version of
GNU make they appear? I think they work in 1.80, correct?
Here is what I tried:

% uname -a
SunOS volga2 5.9 Generic_112233-07 sun4u sparc SUNW,Ultra-60
% gmake -version
GNU Make version 3.74-96q4, by Richard Stallman and Roland McGrath.
Copyright (C) 1988, 89, 90, 91, 92, 93, 94, 95 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.

% cat Makefile
d=${CURDIR}
m=${MAKEFILE_LIST}

all:
        echo "Directory = $d"
        echo "CURDIR=${CURDIR}"
        echo "Makefile = $m"
        echo "MAKEFILE_LIST=${MAKEFILE_LIST}"

% gmake
echo "Directory = "
Directory =
echo "CURDIR="
CURDIR=
echo "Makefile = "
Makefile =
echo "MAKEFILE_LIST="
MAKEFILE_LIST=


There is a standard env. variable ${PWD}, which contains the path
to the current directory. It is supported by Solaris make, GNU
make, and some other make utilities.

Yes, it is possible, but it makes for a barrage of gunk that is all the more unfortunate because it has to be at the top of the Makefile.  Below is what I came up with for an intermediary included Makefile.  The proposed built-in variable would eliminate all of this clutter.

#---------------------------------------------------------
# Find the parent directory of this file.
# Requires make version 3.80 or later.

# Get the pathname of this file
this := $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
# Extract the directory part of that path.
ifeq (/,$(findstring /,$(this)))
    # Remove the last slash and everything after it.
    parentDir := $(shell x=$(this) && echo $${x%/*})
else
    parentDir := .
endif

#---------------------------------------------------------

include $(parentDir)/../../../../Makefile-include

I suppose if I do this only from an included file, I'll be OK.  But in the general case, you can't get the current file path from MAKEFILE_LIST.

Consider a Makefile that starts thus:

    root := ../../..
    include ../../../Makefile-master

It would be nice if this included Makefile-master knew where it was, so it could do something like this:

    root := $(MAKEFILE-PARENT-DIR)
   
    classesDir := $(root)/classes

Having to explicitly set the 'root' variable in the top-level Makefile is a workaround that works, but it would be nice if the workaround could be eliminated.

A shell script can know where it is and what its name is.  The same should be true for Makefiles.  Here's how I do it in sh:

commandDir=${0%/*}
commandName=${0##*/}
if [[ "$commandDir" = "$commandName" ]] ; then
commandDir=.
fi