dockerfile: fix comment regex to preserve line continuation backslash

Change the comment regex from /#.*/ to /#[^\\\n]*(?:\\.[^\\\n]*)*/
so that a trailing backslash on a comment line is NOT consumed as part
of the comment token.

Author: dinaabezgauz-source

fyi/semgrep-grammars/src/tree-sitter-dockerfile/grammar.js

@@ -493,6 +493,6 @@ module.exports = grammar({
 
     _non_newline_whitespace: () => token.immediate(/[\t ]+/),
 
-    comment: () => /#.*/,
+    comment: () => /#[^\\\n]*(?:\\.[^\\\n]*)*/,
   },
 });

lib/Boilerplate.ml

@@ -1085,7 +1085,8 @@ let map_source_file (env : env) (xs : CST.source_file) =
   ) xs)
 
 let map_comment (env : env) (tok : CST.comment) =
-  (* pattern #.* *) token env tok
+  (* pattern #[^\\\n]*(?:\\.[^\\\n]*\
+  )* *) token env tok
 
 let map_line_continuation (env : env) (tok : CST.line_continuation) =
   (* pattern \\[ \t]*\n *) token env tok

lib/CST.ml

@@ -541,7 +541,9 @@ and onbuild_instruction = (pat_onbu * instruction)
 
 type source_file = (instruction * Token.t (* "\n" *)) list (* zero or more *)
 
-type comment (* inlined *) = Token.t (* pattern #.* *)
+type comment (* inlined *) =
+  Token.t (* pattern #[^\\\n]*(?:\\.[^\\\n]*
+  )* *)
 
 type line_continuation (* inlined *) = Token.t (* pattern \\[ \t]*\n *)