dir_PRIMARY_*FLAGS

[NightStrike]

Currently, it's possible to define flags for the general case and for
specific targets.  For instance, the following:

AM_CFLAGS = -flag1

foo_LIBRARIES = liba.a libb.a
liba_a_SOURCES = a.c
liba_a_CFLAGS = $(AM_CFLAGS) -flag2

libb_a_SOURCES = b.c
libb_b_CFLAGS = $(AM_CFLAGS) -flag3

However, is it possible to define flags common to a directory?  For
instance, say both liba and libb needed flag 2.  I'd have to write:

liba_a_CFLAGS = $(AM_CFLAGS) -flag2
libb_b_CFLAGS = $(AM_CFLAGS) -flag2 -flag3

Is it possible to specify something like foo_CFLAGS for all libraries
that get installed into that directory, but not affect the general
case?  Now yes, I can define my own variable called as such and
include it on the CFLAGS line of every library installed into foo.  I
am looking for a more automated way, however.