Move build logic to lib (#97)

* refactored out build to lib

* save_raw returns

* fix indentations and other small fixes

* fix build API

* rename Target to SourceTarget

* fix formatting

* make join runtime_type into runtime_type and runtime_version

cli/build/source.rs

@@ -3,12 +3,7 @@
 pub const UNKNOWN_TRIPLET: &str = "wasm32-unknown-unknown";
 pub const EMSCRIPTEN_TRIPLET: &str = "wasm32-unknown-emscripten";
 
-/// Target configiration of previous build step
-#[derive(Debug, Clone, Copy)]
-pub enum SourceTarget {
-	Emscripten,
-	Unknown,
-}
+use utils::SourceTarget;
 
 /// Configuration of previous build step (cargo compilation)
 #[derive(Debug)]
@@ -59,4 +54,4 @@ impl<'a> SourceInput<'a> {
 	pub fn target(&self) -> SourceTarget {
 		self.target
 	}
-}
+}