update run-make test

Author: jyn514

src/librustdoc/lib.rs

@@ -577,7 +577,7 @@ fn opts() -> Vec<RustcOptGroup> {
             "",
             "merge-doctests",
             "Force all doctests to be compiled as a single binary, instead of one binary per test. If merging fails, rustdoc will emit a hard error.",
-            "",
+            "yes|no|auto",
         ),
         opt(
             Unstable,

tests/run-make/rustdoc-default-output/output-default.stdout

@@ -154,6 +154,10 @@ Options:
                         Comma separated list of types of output for rustdoc to
                         emit
         --no-run        Compile doctests without running them
+        --merge-doctests yes|no|auto
+                        Force all doctests to be compiled as a single binary,
+                        instead of one binary per test. If merging fails,
+                        rustdoc will emit a hard error.
         --remap-path-prefix FROM=TO
                         Remap source names in compiler messages
         --show-type-layout