fix openbsd sofia build

libs/sofia-sip/configure.ac

@@ -100,13 +100,16 @@ if test "x${ax_cv_c_compiler_vendor}"  =  "xsun" ; then
     fi
 fi
 
+SOFIA_PLAT_CFLAGS=
 # openbsd seems to not define NULL as a void pointer, I blame standards by committee for this.
 # This is a dirty hack, but shuts up all the warnings
 case "$host" in
-     *-openbsd*) SOFIA_CFLAGS="$SOFIA_CFLAGS -DNULL='(void *) 0L'";;
+     *-openbsd*) SOFIA_PLAT_CFLAGS="-DNULL='(void *) 0L'";;
      *) ;;
 esac
 
+AC_SUBST(SOFIA_PLAT_CFLAGS, $SOFIA_PLAT_CFLAGS)
+
 
 ### checks for header files
 ### -----------------------

libs/sofia-sip/libsofia-sip-ua/sofia.am

@@ -1,7 +1,7 @@
 # common Makefile targets for libsofia-sip-ua modules
 # ---------------------------------------------------
 
-AM_CFLAGS = $(CWFLAG) $(SOFIA_CFLAGS) $(SOFIA_COVERAGE)
+AM_CFLAGS = $(CWFLAG) $(SOFIA_CFLAGS) $(SOFIA_COVERAGE) $(SOFIA_PLAT_CFLAGS)
 
 # Use with --enable-ndebug
 if NDEBUG

libs/sofia-sip/rules/sofia.am

@@ -4,7 +4,7 @@
 sofiasrcdir = ${top_srcdir}/libsofia-sip-ua
 sofiabuilddir = ${top_builddir}/libsofia-sip-ua
 
-AM_CFLAGS = $(CWFLAG) $(SOFIA_COVERAGE) $(SOFIA_CFLAGS) $(openssl_CFLAGS)
+AM_CFLAGS = $(CWFLAG) $(SOFIA_COVERAGE) $(SOFIA_CFLAGS) $(openssl_CFLAGS) $(SOFIA_PLAT_CFLAGS)
 
 SOFIA_COVERAGE = $(COVERAGE_FLAGS)