Respect CFLAGS when building lrslib (autotools)

Upstream uses CFLAGS to pass the -I${ARITH} flag, so we pass need to
manually include it.

Also move CPPFLAGS from INCLUDEDIR to CC, sine INCLUDEDIR isn't always
used.

Author: d-torrance

M2/libraries/lrslib/Makefile.in

@@ -14,8 +14,10 @@ STRIPFILES = $(PROGRAMS)
 LICENSEFILES = COPYING
 CONFIGURECMD = true
 BUILDTARGET = lrs
-BUILDOPTIONS = CC="$(CC)" LIBDIR="$(BUILTLIBPATH)/lib $(LDFLAGS)" \
-	INCLUDEDIR="$(BUILTLIBPATH)/include $(CPPFLAGS)"
+BUILDOPTIONS = CC="$(CC) $(CPPFLAGS)"           \
+	LIBDIR="$(BUILTLIBPATH)/lib $(LDFLAGS)" \
+	INCLUDEDIR="$(BUILTLIBPATH)/include"    \
+	CFLAGS="$(CFLAGS) -Ilrsarith-011"
 INSTALLCMD = true
 CHECKCMD = true
 include ../Makefile.library