also, I needed to patch openal-soft with:
diff --git a/audio/openal-soft/Makefile b/audio/openal-soft/Makefile
index a7fa2da..4089fb1 100644
--- a/audio/openal-soft/Makefile
+++ b/audio/openal-soft/Makefile
@@ -36,6 +36,9 @@ CMAKE_ARGS+= -DALSOFT_BACKEND_JACK:BOOL=OFF
CMAKE_ARGS+= -DALSOFT_BACKEND_PORTAUDIO:BOOL=OFF
CMAKE_ARGS+= -DALSOFT_BACKEND_PULSEAUDIO:BOOL=OFF
+CFLAGS.SunOS+= -D__EXTENSIONS__
+CMAKE_ARGS+= -DCMAKE_C_FLAGS=${CFLAGS:Q}
+
.include "../../mk/oss.buildlink3.mk"
.if !empty(BUILTIN_LIB_FOUND.ossaudio:M[Yy][Ee][Ss])
to get a working build on SunOS i386.