linker: add link_relative()

src/linker.rs

@@ -47,6 +47,20 @@ impl Linker {
         Ok(bytecode)
     }
 
+    pub fn link_relative(self, symbol: &String) -> Result<Vec<AssemblyWord>, LinkError> {
+        Ok(self.link_partial()?
+            .into_iter()
+            .map(|w| match w {
+                AssemblyWord::Symbol(LinkAddr::Absolute(addr)) =>
+                    AssemblyWord::Symbol(LinkAddr::Relative {
+                        symbol: symbol.clone(),
+                        offset: addr
+                    }),
+                w => w
+            })
+            .collect())
+    }
+
     pub fn link_total(self) -> Result<Vec<VM_Word>, LinkError> {
         self.link_partial()?
             .into_iter()