AM_CPPFLAGS don't appear in cygwin CC line

[Thomas 'Tom' R. Treadway III]

I using automake-1.8.2, (autoconf-2.59, libtool-1.5)
I have a makefile with:

AM_CPPFLAGS = \
 -I$(includedir)

running make on every machine I've tried, generates something like:
gcc -DHAVE_CONFIG_H -I. -I. -I.. -I/usr/tmp/include -g -c sstruct.c

but, the cygwin machine generates:
gcc -g sstruct.c -o sstruct

Are there known issues with cygwin, and automake-1.8.2?

   trt
--
Thomas R. Treadway
Computer Scientist
Lawrence Livermore Nat'l Lab
7000 East Avenue, L-365
Livermore, CA 94550-0611