Create parent directory before writing patch file

We may choose to place the generated `error-prone.patch` file in a
subdirectory of the base which might not already exist. For example, we
may wish to place it in target/patches instead of the base directory.

Fixes #1070

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=311908270

check_api/src/main/java/com/google/errorprone/RefactoringCollection.java

@@ -179,6 +179,7 @@ private static void writePatchFile(
           throw new UncheckedIOException(e);
         }
       }
+      Files.createDirectories(patchFilePatch.getParent());
       Files.write(patchFilePatch, patchFile.getBytes(UTF_8), APPEND, CREATE);
     }
   }