cmd/ebitenmobile: Add linker options

This change suppresses the linker error that the .so file is not
found.

Fixes #932

cmd/ebitenmobile/main.go

@@ -109,6 +109,13 @@ func main() {
 
 	flagset.Parse(args[1:])
 
+	// Add ldflags to suppress linker errors (#932).
+	// See https://github.com/golang/go/issues/17807
+	if buildLdflags == "" {
+		buildLdflags += " "
+	}
+	buildLdflags += "-extldflags=-Wl,-soname,libgojni.so"
+
 	if err := prepareGomobileCommands(); err != nil {
 		log.Fatal(err)
 	}