Use the rust-std manifest file in build_llvm_sysroot_for_triple

This is far more accurate than filtering based on filename and as such
allows building the sysroot a bit quicker. In addition the code is a bit
simpler.

Author: bjorn3

build_system/build_sysroot.rs

@@ -161,35 +161,18 @@ fn build_sysroot_for_triple(
 fn build_llvm_sysroot_for_triple(compiler: Compiler) -> SysrootTarget {
     let default_sysroot = crate::rustc_info::get_default_sysroot(&compiler.rustc);
 
-    let mut target_libs = SysrootTarget { triple: compiler.triple, libs: vec![] };
-
-    for entry in fs::read_dir(
-        default_sysroot.join("lib").join("rustlib").join(&target_libs.triple).join("lib"),
-    )
-    .unwrap()
-    {
-        let entry = entry.unwrap();
-        if entry.file_type().unwrap().is_dir() {
-            continue;
-        }
-        let file = entry.path();
-        let file_name_str = file.file_name().unwrap().to_str().unwrap();
-        if (file_name_str.contains("rustc_")
-            && !file_name_str.contains("rustc_std_workspace_")
-            && !file_name_str.contains("rustc_demangle")
-            && !file_name_str.contains("rustc_literal_escaper"))
-            || file_name_str.contains("chalk")
-            || file_name_str.contains("tracing")
-            || file_name_str.contains("regex")
-        {
-            // These are large crates that are part of the rustc-dev component and are not
-            // necessary to run regular programs.
-            continue;
-        }
-        target_libs.libs.push(file);
-    }
-
-    target_libs
+    let std_manifest_path = default_sysroot
+        .join("lib")
+        .join("rustlib")
+        .join(format!("manifest-rust-std-{}", compiler.triple));
+
+    let libs = fs::read_to_string(std_manifest_path)
+        .unwrap()
+        .lines()
+        .map(|entry| default_sysroot.join(entry.strip_prefix("file:").unwrap()))
+        .collect();
+
+    SysrootTarget { triple: compiler.triple, libs }
 }
 
 fn build_clif_sysroot_for_triple(