configure.ac: avoid spaces in a LDFLAGS option

Seems like it confuses "make ruby" for emscripten.

configure.ac

@@ -1176,8 +1176,8 @@ main()
 		])
 		],
 [emscripten*], [LIBS="-lm -lc $LIBS"
-		RUBY_APPEND_OPTIONS(LDFLAGS, "-s ALLOW_MEMORY_GROWTH=1")
-		RUBY_APPEND_OPTIONS(LDFLAGS, "-s ASYNCIFY")
+		RUBY_APPEND_OPTIONS(LDFLAGS, "-sALLOW_MEMORY_GROWTH=1")
+		RUBY_APPEND_OPTIONS(LDFLAGS, "-sASYNCIFY")
 		],
 [	LIBS="-lm $LIBS"])
 : ${ORIG_LIBS=$LIBS}