wasm: emit Emscripten metadata (for ABI).

test/extensions/filters/http/wasm/test_data/Makefile

@@ -1,21 +1,24 @@
+API=../../../../../../api/wasm/cpp
+
+EMSCRIPTEN_OPT=-s WASM=1 -s EMIT_EMSCRIPTEN_METADATA=1
+
 # Note that optimizations are disabled, because optimized WASM module
 # throws wavm.integerDivideByZeroOrOverflow, possibly due to an issue
 # with getFunctionWavm() templates and/or their usage.
-#OPT=-O3
-OPT=
-API=../../../../../../api/wasm/cpp
+#CXXFLAGS=--std=c++14 -O3 -g3
+CXXFLAGS=--std=c++14 -g3
 
 all: headers.wasm async_call.wasm
 
 headers.wasm headers.wat: headers.cc ${API}/proxy_wasm_intrinsics.h ${API}/proxy_wasm_intrinsics.cc ${API}/proxy_wasm_intrinsics.js
-	em++ -s WASM=1 --std=c++14 $(OPT) -g3 -I${API} --js-library ${API}/proxy_wasm_intrinsics.js headers.cc ${API}/proxy_wasm_intrinsics.cc -o headers.js
+	em++ ${EMSCRIPTEN_OPT} ${CXXFLAGS} -I${API} --js-library ${API}/proxy_wasm_intrinsics.js headers.cc ${API}/proxy_wasm_intrinsics.cc -o headers.js
 	wasm-gc headers.wasm
 	wavm-disas headers.wasm headers.wat
 	rm -f headers.js headers.wast
 	chmod 644 headers.wat
 
 async_call.wasm async_call.wat: async_call.cc ${API}/proxy_wasm_intrinsics.h ${API}/proxy_wasm_intrinsics.cc ${API}/proxy_wasm_intrinsics.js
-	em++ -s WASM=1 --std=c++14 $(OPT) -g3 -I${API} --js-library ${API}/proxy_wasm_intrinsics.js async_call.cc ${API}/proxy_wasm_intrinsics.cc -o async_call.js
+	em++ ${EMSCRIPTEN_OPT} ${CXXFLAGS} -I${API} --js-library ${API}/proxy_wasm_intrinsics.js async_call.cc ${API}/proxy_wasm_intrinsics.cc -o async_call.js
 	wasm-gc async_call.wasm
 	wavm-disas async_call.wasm async_call.wat
 	rm -f async_call.js async_call.wast