Auto merge of #131188 - Kobzol:remove-libstd-so-from-sysroot, r=onur-ozkan

Do not copy libstd dynamic library to sysroot

Since https://github.com/rust-lang/rust/pull/122362, rustc links statically to libstd.[so|dll]. Which means that the libstd.[so|dll] file no longer has to be in the rustc sysroot. However, we are currently still shipping this file, in every new release of Rust, for no reason, it's just wasted bytes.

This PR removes the dynamic library file from the built sysroot.

However, it is not yet performed on Windows, because stage0 incremental tests start failing there (see description of the issue [here](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Failing.20incr.20tests.20on.20Windows.20when.20std.2Edll.20is.20missing/near/474507064)).

This is an extended version of https://github.com/rust-lang/rust/pull/128986.
CC `@Zoxc`

src/bootstrap/src/bin/rustc.rs

@@ -95,7 +95,6 @@ fn main() {
     // When statically linking `std` into `rustc_driver`, remove `-C prefer-dynamic`
     if env::var("RUSTC_LINK_STD_INTO_RUSTC_DRIVER").unwrap() == "1"
         && crate_name == Some("rustc_driver")
-        && stage != "0"
     {
         if let Some(pos) = args.iter().enumerate().position(|(i, a)| {
             a == "-C" && args.get(i + 1).map(|a| a == "prefer-dynamic").unwrap_or(false)

src/bootstrap/src/core/build_steps/compile.rs

@@ -1923,8 +1923,24 @@ impl Step for Assemble {
         let src_libdir = builder.sysroot_libdir(build_compiler, host);
         for f in builder.read_dir(&src_libdir) {
             let filename = f.file_name().into_string().unwrap();
-            if (is_dylib(&filename) || is_debug_info(&filename)) && !proc_macros.contains(&filename)
+
+            let is_proc_macro = proc_macros.contains(&filename);
+            let is_dylib_or_debug = is_dylib(&filename) || is_debug_info(&filename);
+
+            // If we link statically to stdlib, do not copy the libstd dynamic library file
+            // FIXME: Also do this for Windows once incremental post-optimization stage0 tests
+            // work without std.dll (see https://github.com/rust-lang/rust/pull/131188).
+            let can_be_rustc_dynamic_dep = if builder
+                .link_std_into_rustc_driver(target_compiler.host)
+                && !target_compiler.host.is_windows()
             {
+                let is_std = filename.starts_with("std-") || filename.starts_with("libstd-");
+                !is_std
+            } else {
+                true
+            };
+
+            if is_dylib_or_debug && can_be_rustc_dynamic_dep && !is_proc_macro {
                 builder.copy_link(&f.path(), &rustc_libdir.join(&filename));
             }
         }

tests/ui/command/command-current-dir.rs

@@ -1,4 +1,5 @@
 //@ run-pass
+//@ no-prefer-dynamic We move the binary around, so do not depend dynamically on libstd
 //@ ignore-wasm32 no processes
 //@ ignore-sgx no processes
 //@ ignore-fuchsia Needs directory creation privilege