rustdoc use -Ccodegen-units=1 by default for test compile

as the test is small we do not want split up in multiple codegen units
and also as there is multiple test running at the same time this
will reduce the number of concurrent threads

1 files changed, 1 insertions, 0 deletions

diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 31c0b85a481..88397aacac1 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -263,6 +263,7 @@ fn run_test(
     for extern_str in &options.extern_strs {
         compiler.arg("--extern").arg(&extern_str);
     }
+    compiler.arg("-Ccodegen-units=1");
     for codegen_options_str in &options.codegen_options_strs {
         compiler.arg("-C").arg(&codegen_options_str);
     }