Checks for the varieties of MAKE, including support for VPATH
Sets MAKE to the make program to use if MAKE is not already set.
Sets the variable SET_CFLAGS to CFLAGS = if make sets CFLAGS.
This macro uses PAC_PROG_MAKE_ECHOS_DIR, PAC_PROG_MAKE_INCLUDE,
PAC_PROG_MAKE_ALLOWS_COMMENTS, PAC_PROG_MAKE_VPATH, and
PAC_PROG_MAKE_SET_CFLAGS. See those commands for details about their
It may call AC_PROG_MAKE_SET, which sets SET_MAKE to MAKE = @MAKE@
if the make program does not set the value of make, otherwise SET_MAKE
is set to empty; if the make program echos the directory name, then
SET_MAKE is set to MAKE = $MAKE.