WASI: Switch to crt1-command.o to enable support for new-style commands

This switches Rust's WASI target to use crt1-command.o instead of
crt1.o, which enables support for new-style commands. By default,
new-style commands work the same way as old-style commands, so nothing
immediately changes here, but this will be needed by later changes to
enable support for typed arguments.

See here for more information on new-style commands:
 - WebAssembly/wasi-libc#203
 - https://reviews.llvm.org/D81689

compiler/rustc_target/src/spec/crt_objects.rs

@@ -108,11 +108,13 @@ pub(super) fn post_mingw() -> CrtObjects {
 }
 
 pub(super) fn pre_wasi_fallback() -> CrtObjects {
+    // Use crt1-command.o instead of crt1.o to enable support for new-style
+    // commands. See https://reviews.llvm.org/D81689 for more info.
     new(&[
-        (LinkOutputKind::DynamicNoPicExe, &["crt1.o"]),
-        (LinkOutputKind::DynamicPicExe, &["crt1.o"]),
-        (LinkOutputKind::StaticNoPicExe, &["crt1.o"]),
-        (LinkOutputKind::StaticPicExe, &["crt1.o"]),
+        (LinkOutputKind::DynamicNoPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::DynamicPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::StaticNoPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::StaticPicExe, &["crt1-command.o"]),
         (LinkOutputKind::WasiReactorExe, &["crt1-reactor.o"]),
     ])
 }

src/bootstrap/compile.rs

@@ -210,7 +210,7 @@ fn copy_self_contained_objects(
                 panic!("Target {:?} does not have a \"wasi-root\" key", target.triple)
             })
             .join("lib/wasm32-wasi");
-        for &obj in &["crt1.o", "crt1-reactor.o"] {
+        for &obj in &["crt1-command.o", "crt1-reactor.o"] {
             copy_and_stamp(
                 builder,
                 &libdir_self_contained,