Stop converting relative symlinks to absolute.

There's no reason to make them absolute, simply store in the metadata
the target file as is. This vastly simplifies the code and makes all
test pass correctly.

NEWS

@@ -3,7 +3,9 @@ xbps-0.44 (???):
  * xbps-pkgdb(8): this now uses the code from libxbps to check the target file
    of symlinks. This fixes some false positives with symlinks.
 
- * xbps-create(8): properly detect target of relative symlinks in some cases.
+ * xbps-create(8): relative target file of symlinks aren't converted to absolute
+   anymore. This just stores what the symlink points to, does not matter if
+   it's relative or absolute path.
 
  * libxbps: make sure that symlinks with relative target are detected and removed
    properly. Fix #78: https://github.com/voidlinux/xbps/issues/78