fix(es/codegen): Fix source map so it works with Sentry (#9627)

**Description:**

Fix web-infra-dev/rspack#7914

The following mapping is redundant and causes an error on Sentry.


![image](https://github.com/user-attachments/assets/0d3067d9-6adb-4434-aa84-6ed73a71fdad)

```
Your source map refers to generated column 79 on line 1, but the source only contains 78 column(s) on that line.
```

Author: SyMind

.changeset/wise-laws-wash.md

@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc_ecma_codegen: patch
+---
+
+fix: source map is not working on Sentry

crates/swc/tests/fixture/sourcemap/issue-9567/output/index.map

@@ -1,5 +1,5 @@
 {
-  "mappings": "AAAA,SAASA,EAAIC,CAAI,CAAEC,CAAK,EACtBD,EAAKE,SAAS,CAAC,CACXC,QAAS,CAAC,EAAEF,EAAME,OAAO,CAAC,CAAC,EACvBF,EAAMG,IAAI,CACJ,CAAC;AAAE;AAAS;AAC5B;AAAS;AACT;AAAI,GAAG,EAAEH,EAAMG,IAAI,CAAC,CAAC,CACL,QACT,CAAC,AACN,EACF,CACAL",
+  "mappings": "AAAA,SAASA,EAAIC,CAAI,CAAEC,CAAK,EACtBD,EAAKE,SAAS,CAAC,CACXC,QAAS,CAAC,EAAEF,EAAME,OAAO,CAAC,CAAC,EACvBF,EAAMG,IAAI,CACJ;AAAG;AAAS;AAC5B;AAAS;AACT;AAAI,GAAG,EAAEH,EAAMG,IAAI,CAAC,CAAC,CACL,QACT,CAAC,AACN,EACF,CACAL",
   "names": [
     "foo",
     "span",

crates/swc_ecma_codegen/src/lib.rs

@@ -1994,8 +1994,13 @@ where
                 .match_indices('\n')
                 .zip(NEW_LINE_TPL_REGEX.find_iter(&raw))
             {
-                self.wr
-                    .add_srcmap(span.lo + BytePos(last_offset_origin as u32))?;
+                // If the string starts with a newline char, then adding a mark is redundant.
+                // This catches both "no newlines" and "newline after several chars".
+                if offset_gen != 0 {
+                    self.wr
+                        .add_srcmap(span.lo + BytePos(last_offset_origin as u32))?;
+                }
+
                 self.wr
                     .write_str_lit(DUMMY_SP, &v[last_offset_gen..=offset_gen])?;
                 last_offset_gen = offset_gen + 1;