The current behavior is correct. (Otherwise all of the -Xswiftc arguments would have to go at the end, and there is more than one -X option that you might want to pass.)

Comment by Amr Aboelela (JIRA)

But there got to be a better solution, because imagine I want to add: -emit-library -o libSwiftLevelDB.so
Currently it has to be:
swift build -v -Xswiftc -DDEBUG \
-Xswiftc -emit-library -Xswiftc -o -Xswiftc libSwiftLevelDB.so

-Xswiftc is a hack to make up for not having build settings. You certainly shouldn't use it to control things like -emit-library or -o; it'll confuse the package manager.

Comment by Amr Aboelela (JIRA)

Well I tried it and it works 🙂
What is the right solution then?

You tried it and it builds. What are you actually trying to do?

(and, tagging in @aciidb0mb3r, who knows a lot more about the package manager and swift-build than I do.)

@belkadan is right, -Xswiftc is a hack until we get build settings. The arguments are passed directly to all the packages in the graph. Do not rely on this to create things like libraries. See SE-0146 if you want to create a library product. It is implemented in trunk so you can grab a trunk toolchain from swift.org to try it out. (Also see SE-0158 for Swift 4 manifest syntax).

Comment by Amr Aboelela (JIRA)

Ok, got it.