rustc: Allow the cdylib crate type with wasm32-wasi

The wasm32-wasi target respects configuration around `crt-static` in
general, but is defaulted to being static. This interacted badly with
code which validated the `cdylib` crate type for `wasm32-wasi`,
erroneously saying that the `cdylib` crate type wasn't supported on
`wasm32-wasi` by default. This commit sets the appropriate flag in
`wasm32_wasi`'s target specification to indicate that the `cdylib` crate
type is supported regardless of `crt-static`

Closes #64187

Author: alexcrichton

src/librustc_target/spec/wasm32_wasi.rs

@@ -97,6 +97,10 @@ pub fn target() -> Result<Target, String> {
     options.crt_static_default = true;
     options.crt_static_respected = true;
 
+    // Allow `+crt-static` to create a "cdylib" output which is just a wasm file
+    // without a main function.
+    options.crt_static_allows_dylibs = true;
+
     Ok(Target {
         llvm_target: "wasm32-wasi".to_string(),
         target_endian: "little".to_string(),