Specifying include directories for groups of source files

[William S Fulton <wsf at fultondesigns dot co dot uk>]

A question about groups of files in subdirectories. I would like 
Automake's generated Makefiles to compile groups of files using 
different include directories, that is, different INCLUDES (AM_CFLAGS) 
for each group. Each group is in a different subdirectory. Is this 
possible without using the _LIBRARIES or _LTLIBRARIES primary?

Motivation: We don't want to use libtool and having a separate 
Makefile.am each with its own _LIBRARIES does not work on all platforms, 
notably using native Windows compilers. This is what I have at the 
moment, but it uses the same INCLUDES for all groups:

# Makefile.am
INCLUDES = -I$(top_srcdir)/Group1/Include -I$(top_srcdir)/Group2
group1 = Group1/file1.c Group1/file2.c
group2 = Group2/fileA.c Group2/fileB.c
bin_PROGRAMS =  myprog
myprog_SOURCES = $(group1) $(group2)

Thanks
William