Add .gitignore section for additional test build files

[ci skip]

For now this is only for the bad_cmd.exe, but we may add more entries.

Closes phpGH-17753.

Author: ndossche

.gitignore

@@ -291,6 +291,11 @@ tmp-php.ini
 /junit.out.xml
 /.ccache/
 
+# ------------------------------------------------------------------------------
+# Additional test build files
+# ------------------------------------------------------------------------------
+/ext/standard/tests/helpers/bad_cmd.exe
+
 # ------------------------------------------------------------------------------
 # Special cases to invert previous ignore patterns
 # ------------------------------------------------------------------------------