Stop linking rs{begin,end} on x86_64-*-windows-gnu

Until now, x86_64-pc-windows-gnu linked `rsbegin.o` and `rsend.o` just
like i686-pc-windows-gnu, even though they were no-ops for it.
This was likely done for the simplicity back when it was introduced.

Today the things are different and these startup/end objects harm other
features, like `build-std`. Given the demotion of i686-pc-windows-gnu
from tier 1, there is no point in hurting x86_64-pc-windows-gnu,
which remains a tier 1.

The files are still shipped in case downstream crates expect them, as in
case of the unmaintained `xargo`.

compiler/rustc_target/src/spec/base/windows_gnu.rs

@@ -93,10 +93,7 @@ pub(crate) fn opts() -> TargetOptions {
         binary_format: BinaryFormat::Coff,
         allows_weak_linkage: false,
         pre_link_args,
-        pre_link_objects: crt_objects::pre_mingw(),
-        post_link_objects: crt_objects::post_mingw(),
         pre_link_objects_self_contained: crt_objects::pre_mingw_self_contained(),
-        post_link_objects_self_contained: crt_objects::post_mingw_self_contained(),
         link_self_contained: LinkSelfContainedDefault::InferredForMingw,
         late_link_args,
         late_link_args_dynamic,

compiler/rustc_target/src/spec/crt_objects.rs

@@ -85,6 +85,17 @@ pub(super) fn post_musl_self_contained() -> CrtObjects {
 }
 
 pub(super) fn pre_mingw_self_contained() -> CrtObjects {
+    new(&[
+        (LinkOutputKind::DynamicNoPicExe, &["crt2.o"]),
+        (LinkOutputKind::DynamicPicExe, &["crt2.o"]),
+        (LinkOutputKind::StaticNoPicExe, &["crt2.o"]),
+        (LinkOutputKind::StaticPicExe, &["crt2.o"]),
+        (LinkOutputKind::DynamicDylib, &["dllcrt2.o"]),
+        (LinkOutputKind::StaticDylib, &["dllcrt2.o"]),
+    ])
+}
+
+pub(super) fn pre_i686_mingw_self_contained() -> CrtObjects {
     new(&[
         (LinkOutputKind::DynamicNoPicExe, &["crt2.o", "rsbegin.o"]),
         (LinkOutputKind::DynamicPicExe, &["crt2.o", "rsbegin.o"]),
@@ -95,15 +106,15 @@ pub(super) fn pre_mingw_self_contained() -> CrtObjects {
     ])
 }
 
-pub(super) fn post_mingw_self_contained() -> CrtObjects {
+pub(super) fn post_i686_mingw_self_contained() -> CrtObjects {
     all("rsend.o")
 }
 
-pub(super) fn pre_mingw() -> CrtObjects {
+pub(super) fn pre_i686_mingw() -> CrtObjects {
     all("rsbegin.o")
 }
 
-pub(super) fn post_mingw() -> CrtObjects {
+pub(super) fn post_i686_mingw() -> CrtObjects {
     all("rsend.o")
 }
 

compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs

@@ -1,4 +1,6 @@
-use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, RustcAbi, Target, TargetMetadata, base};
+use crate::spec::{
+    Cc, FramePointer, LinkerFlavor, Lld, RustcAbi, Target, TargetMetadata, base, crt_objects,
+};
 
 pub(crate) fn target() -> Target {
     let mut base = base::windows_gnu::opts();
@@ -15,6 +17,10 @@ pub(crate) fn target() -> Target {
         &["-m", "i386pe", "--large-address-aware"],
     );
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-Wl,--large-address-aware"]);
+    base.pre_link_objects = crt_objects::pre_i686_mingw();
+    base.post_link_objects = crt_objects::post_i686_mingw();
+    base.pre_link_objects_self_contained = crt_objects::pre_i686_mingw_self_contained();
+    base.post_link_objects_self_contained = crt_objects::post_i686_mingw_self_contained();
 
     Target {
         llvm_target: "i686-pc-windows-gnu".into(),

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

@@ -895,6 +895,8 @@ impl Step for StartupObjects {
     fn run(self, builder: &Builder<'_>) -> Vec<(PathBuf, DependencyType)> {
         let for_compiler = self.compiler;
         let target = self.target;
+        // Even though no longer necessary on x86_64, they are kept for now to
+        // avoid potential issues in downstream crates.
         if !target.is_windows_gnu() {
             return vec![];
         }