NSIS: When extracting files, get the path's basename when recording the name

In the scan metadata JSON, the result will be like this:
```json
        {
          "FileName":"headers",
          "FilePath":"/home/micah/tmp/20250702_173504-clam-nsis.exe.991ca413f9/clamav-b8d49de1082953f591c02163a128b90b.tmp/nulsft-tmp.1416a98706/headers",
          "FileSize":4357,
          "ObjectID":2
        },
```
... instead of this:
```json
        {
          "FileName":"/home/micah/tmp/20250702_172320-clam-nsis.exe.1bfb389b2c/clamav-41fa5f1bc556577438b143bc2915f57c.tmp/nulsft-tmp.a851a869ee/headers",
          "FilePath":"/home/micah/tmp/20250702_172320-clam-nsis.exe.1bfb389b2c/clamav-41fa5f1bc556577438b143bc2915f57c.tmp/nulsft-tmp.a851a869ee/headers",
          "FileSize":4357,
          "ObjectID":2
        },
```json

Author: val-ms

libclamav/nsis/nulsft.c

@@ -539,18 +539,31 @@ int cli_scannulsft(cli_ctx *ctx, off_t offset)
             continue;
         }
         if (ret == CL_SUCCESS) {
+            char *name = NULL;
             cli_dbgmsg("NSIS: Successfully extracted file #%u\n", nsist.fno);
             if (lseek(nsist.ofd, 0, SEEK_SET) == -1) {
                 cli_dbgmsg("NSIS: call to lseek() failed\n");
                 free(nsist.dir);
                 return CL_ESEEK;
             }
+
+            // Get basename of the file from nsist.ofn
+            ret = cli_basename(nsist.ofn, strlen(nsist.ofn), &name);
+            if (CL_SUCCESS != ret || NULL == name) {
+                cli_dbgmsg("NSIS: Failed to get basename of the file\n");
+                // If it fails, the name will just be NULL. That's okay.
+            }
+
             if (nsist.fno == 1) {
-                ret = cli_scan_desc(nsist.ofd, ctx, CL_TYPE_ANY, false, NULL, AC_SCAN_VIR, NULL, nsist.ofn, nsist.ofn, LAYER_ATTRIBUTES_NONE); /// TODO: Extract file names
+                ret = cli_scan_desc(nsist.ofd, ctx, CL_TYPE_ANY, false, NULL, AC_SCAN_VIR, NULL, name, nsist.ofn, LAYER_ATTRIBUTES_NONE); /// TODO: Extract file names
             } else {
-                ret = cli_magic_scan_desc(nsist.ofd, nsist.ofn, ctx, nsist.ofn, LAYER_ATTRIBUTES_NONE); /// TODO: Extract file names
+                ret = cli_magic_scan_desc(nsist.ofd, nsist.ofn, ctx, name, LAYER_ATTRIBUTES_NONE); /// TODO: Extract file names
             }
+
+            CLI_FREE_AND_SET_NULL(name);
+
             close(nsist.ofd);
+
             if (!ctx->engine->keeptmp) {
                 if (cli_unlink(nsist.ofn)) {
                     ret = CL_EUNLINK;