Target-specific variables have the same priority as any other
makefile variable.  Variables provided on the command line (and in the
environment if the `-e' option is in force) will take precedence.
Specifying the `override' directive will allow the target-specific
variable value to be preferred.

   There is one more special feature of target-specific variables: when
you define a target-specific variable that variable value is also in
effect for all prerequisites of this target, and all their
prerequisites, etc. (unless those prerequisites override that variable
with their own target-specific variable value).  So, for example, a
statement like this:

     prog : CFLAGS = -g
     prog : prog.o foo.o bar.o

will set `CFLAGS' to `-g' in the recipe for `prog', but it will also
set `CFLAGS' to `-g' in the recipes that create `prog.o', `foo.o', and
`bar.o', and any recipes which create their prerequisites.

   Be aware that a given prerequisite will only be built once per
invocation of make, at most.  If the same file is a prerequisite of
multiple targets, and each of those targets has a different value for
the same target-specific variable, then the first target to be built
will cause that prerequisite to be built and the prerequisite will
inherit the target-specific value from the first target.  It will
ignore the target-specific values from any other targets.