compiler: Use --assume-main-file-path as relative path for imports

This PR fixes an issue with IDE integration where the compiler would use
the relative path of the temporary file for imports, rather than the
main file path specified.

selfhost/compiler.jakt

@@ -187,10 +187,7 @@ class Compiler {
     }
 
     public fn find_in_search_paths(this, anon path: Path, relative_import: bool = false, parent_path_count: usize = 0) throws -> Path? {
-        let current_file_path = match relative_import {
-            true => .current_file_path()
-            false => .assume_main_file_path ?? .current_file_path()
-        }
+        let current_file_path = .assume_main_file_path ?? .current_file_path()
         if current_file_path.has_value() {
             mut candidate_path = current_file_path!.absolute().parent()
             if relative_import and parent_path_count > 0 {