Auto merge of #86876 - jyn514:56935-target-crate-num, r=petrochenkov

Reuse CrateNum for proc-macro crates even when cross-compiling

Proc-macros are always compiled for the host, so this should be the same
in every way as recompiling the crate.

I am not sure why the previous code special-cased the target, since the
compiler properly gives an error when trying to load a crate for a
different host:

```
error[E0461]: couldn't find crate `dependency` with expected target triple x86_64-unknown-linux-gnu
  --> /home/joshua/rustc4/src/test/ui/cfg-dependent.rs:8:2
   |
LL |     dependency::is_64();
   |     ^^^^^^^^^^
   |
   = note: the following crate versions were found:
           crate `dependency`, target triple i686-unknown-linux-gnu: /home/joshua/rustc4/build/x86_64-unknown-linux-gnu/test/ui/cfg-dependent/auxiliary/libdependency.so
```

I think another possible fix is to remove the check altogether. But I'm
not sure, and this fix works, so I'm not making the larger change here.

Fixes https://github.com/rust-lang/rust/issues/56935.

r? `@petrochenkov` cc `@alexcrichton`

2 files changed, 20 insertions, 0 deletions

diff --git a/src/test/ui/crate-loading/auxiliary/proc-macro.rs b/src/test/ui/crate-loading/auxiliary/proc-macro.rs
new file mode 100644
index 00000000000..52631de5757
--- /dev/null
+++ b/src/test/ui/crate-loading/auxiliary/proc-macro.rs
@@ -0,0 +1,12 @@
+// force-host
+// no-prefer-dynamic
+#![crate_name = "reproduction"]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn mac(input: TokenStream) -> TokenStream {
+    input
+}
diff --git a/src/test/ui/crate-loading/cross-compiled-proc-macro.rs b/src/test/ui/crate-loading/cross-compiled-proc-macro.rs
new file mode 100644
index 00000000000..c1f4331438e
--- /dev/null
+++ b/src/test/ui/crate-loading/cross-compiled-proc-macro.rs
@@ -0,0 +1,8 @@
+// edition:2018
+// compile-flags:--extern reproduction
+// aux-build:proc-macro.rs
+// check-pass
+
+reproduction::mac!();
+
+fn main() {}