[bonnibel] Add SONAME to shared objects

Add -soname to the linker options when making shared libraries, so that they
have a SONAME string in their DYNAMIC section.

assets/build/rules.ninja

@@ -47,7 +47,7 @@ rule driver
   description = Linking driver [$target]:$name
 
 rule lib
-  command = $ld -shared $ldflags -o $out $in $libs
+  command = $ld -shared -soname $soname $ldflags -o $out $in $libs
   description = Linking [$target]:$name
 
 rule lib_static

scripts/bonnibel/module.py

@@ -298,7 +298,8 @@ class Module:
                 inputs = inputs,
                 implicit = modopts.implicit,
                 order_only = modopts.order_only,
-                variables = {"name": self.name},
+                variables = {"name": self.name,
+                             "soname": self.get_output()},
             )
 
             dump = output + ".dump"