Rollup merge of #92933 - bjorn3:no_bin_lib_mixing, r=estebank

Deny mixing bin crate type with lib crate types

The produced library would get a main shim too which conflicts with the
main shim of the executable linking the library.

```
$ cat > main1.rs <<EOF
fn main() {}
pub fn bar() {}
EOF
$ cat > main2.rs <<EOF
extern crate main1;
fn main() {
    main1::bar();
}
EOF
$ rustc --crate-type bin --crate-type lib main1.rs
$ rustc -L. main2.rs
error: linking with `cc` failed: exit status: 1
[...]
  = note: /usr/bin/ld: /tmp/crate_bin_lib/libmain1.rlib(main1.main1.707747aa-cgu.0.rcgu.o): in function `main':
          main1.707747aa-cgu.0:(.text.main+0x0): multiple definition of `main'; main2.main2.02a148fe-cgu.0.rcgu.o:main2.02a148fe-cgu.0:(.text.main+0x0): first defined here
          collect2: error: ld returned 1 exit status
```

1 files changed, 0 insertions, 5 deletions

diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index 6f61e4cba07..c9dd114047b 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -56,7 +56,6 @@ pub fn inject(
     is_proc_macro_crate: bool,
     has_proc_macro_decls: bool,
     is_test_crate: bool,
-    num_crate_types: usize,
     handler: &rustc_errors::Handler,
 ) -> ast::Crate {
     let ecfg = ExpansionConfig::default("proc_macro".to_string());
@@ -81,10 +80,6 @@ pub fn inject(
         return krate;
     }
 
-    if num_crate_types > 1 {
-        handler.err("cannot mix `proc-macro` crate type with others");
-    }
-
     if is_test_crate {
         return krate;
     }