Automake includes some support for assembly code.
The variable CCAS holds the name of the compiler used to build
assembly code. This compiler must work a bit like a C compiler; in
particular it must accept -c and -o. The value of
CCASFLAGS is passed to the compilation.
You are required to set CCAS and CCASFLAGS via
configure.in. The autoconf macro AM_PROG_AS will do this
for you. Unless they are already set, it simply sets CCAS to the
C compiler and CCASFLAGS to the C compiler flags.
Only the suffixes .s and .S are recognized by
automake as being files containing assembly code.