Add testing infrastructure for libc-0.2.124.

Author: nnethercote

collector/benchmarks/README.md

@@ -33,6 +33,9 @@ They mostly consist of real-world crates.
 - **image-0.24.1**: Basic image processing functions and methods for 
   converting to and from various image formats. Used often in graphics 
   programming.
+- **libc-0.2.124**: An interface to `libc`. Contains many declarations of
+  types, constants, and functions, but relatively little normal code. Stresses
+  the parser. A very widely-used crate.
 - **regex-1.5.5**: A regular expression parser. Used by many Rust programs.
 - **ripgrep-13.0.0**: A line-oriented search tool. A widely-used utility.
 - **serde-1.0.136**: A serialization/deserialization crate. Used by many other

collector/benchmarks/libc-0.2.124/0-clone.patch

@@ -0,0 +1,13 @@
+diff --git a/src/macros.rs b/src/macros.rs
+index 9fb7f7a7..39cbf962 100644
+--- a/src/macros.rs
++++ b/src/macros.rs
+@@ -82,7 +82,7 @@ macro_rules! s {
+         impl ::Copy for $i {}
+         #[allow(deprecated)]
+         impl ::Clone for $i {
+-            fn clone(&self) -> $i { *self }
++            fn clone(&self) -> $i { let x = *self; x }
+         }
+     );
+ }

collector/benchmarks/libc-0.2.124/Cargo.lock

@@ -62,3 +62,5 @@ rustc-dep-of-std = [
 ]
 std = []
 use_std = ["std"]
+
+[workspace]