[SOL] build-std: pull in our compiler-builtins

When -Z build-std is used, patch compiler-builtins so that our own fork is
downloaded.

Needed for solana-labs/solana#23465.

src/cargo/core/compiler/standard_lib.rs

@@ -6,7 +6,7 @@ use crate::core::compiler::{CompileKind, CompileMode, RustcTargetData, Unit};
 use crate::core::profiles::{Profiles, UnitFor};
 use crate::core::resolver::features::{CliFeatures, FeaturesFor, ResolvedFeatures};
 use crate::core::resolver::HasDevUnits;
-use crate::core::{Dependency, PackageId, PackageSet, Resolve, SourceId, Workspace};
+use crate::core::{Dependency, GitReference, PackageId, PackageSet, Resolve, SourceId, Workspace};
 use crate::ops::{self, Packages};
 use crate::util::errors::CargoResult;
 use crate::Config;
@@ -79,14 +79,22 @@ pub fn resolve_std<'cfg>(
         "rustc-std-workspace-alloc",
         "rustc-std-workspace-std",
     ];
-    let patches = to_patch
+    let mut patches = to_patch
         .iter()
         .map(|&name| {
             let source_path = SourceId::for_path(&src_path.join("library").join(name))?;
             let dep = Dependency::parse(name, None, source_path)?;
             Ok(dep)
         })
         .collect::<CargoResult<Vec<_>>>()?;
+    patches.push(Dependency::parse(
+        "compiler_builtins",
+        None,
+        SourceId::for_git(
+            &("https://github.com/solana-labs/compiler-builtins".parse()).unwrap(),
+            GitReference::Tag("sbf-tools-v1.31".to_string()),
+        )?,
+    )?);
     let crates_io_url = crate::sources::CRATES_IO_INDEX.parse().unwrap();
     let patch = HashMap::from([(crates_io_url, patches)]);
     let members = vec![