Add test to ensure passing --doctest_compilation_args multiple times work

Author: GuillaumeGomez

src/doc/rustdoc/src/unstable-features.md

@@ -667,7 +667,7 @@ This flag can be passed multiple times to nest wrappers.
 
 ## Passing arguments to rustc when compiling doctests
 
-You can use the `--doctest-compilation-args` option if you want to add options when compiling the
+You can use the `--doctest-compilation-args` flag if you want to add options when compiling the
 doctest. For example if you have:
 
 ```rust,no_run

tests/rustdoc-ui/doctest/rustflags-multiple-args.rs

@@ -0,0 +1,17 @@
+// This test checks that the test behave when `--doctest-compilation-args` is passed
+// multiple times.
+
+//@ check-pass
+//@ compile-flags: --test -Zunstable-options --doctest-compilation-args=--cfg=testcase_must_be_present
+//@ compile-flags: --doctest-compilation-args=--cfg=another
+//@ normalize-stdout-test: "tests/rustdoc-ui/doctest" -> "$$DIR"
+//@ normalize-stdout-test: "finished in \d+\.\d+s" -> "finished in $$TIME"
+
+/// ```
+/// #[cfg(testcase_must_be_present)]
+/// #[cfg(another)]
+/// fn must_be_present() {}
+///
+/// fn main() { must_be_present() }
+/// ```
+pub struct Bar;

tests/rustdoc-ui/doctest/rustflags-multiple-args.stdout

@@ -0,0 +1,6 @@
+
+running 1 test
+test $DIR/rustflags-multiple-args.rs - Bar (line 10) ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+