fix(es/plugin): use #[cfg] to avoid compilation error (#11316)

**Description:**
#11267 introduced this mistake.
- `SHARED_RUNTIME.block_on(fut)` is enabled with`#[cfg(feature =
"plugin")]`
- `SHARED_RUNTIME` is enabled with `#[cfg(all(feature = "plugin",
not(feature = "manual-tokio-runtime")))]`
- If both features are enabled, the compiler goes failed.

The problem is that cfg! doesn't remove the code actually. `#[cfg]` is
needed here

Author: CPunisher

.changeset/large-waves-clean.md

@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc: patch
+---
+
+fix(es/plugin): use `#[cfg]` to avoid compilation error

crates/swc/src/plugin.rs

@@ -83,23 +83,30 @@ impl RustPlugins {
     #[cfg(feature = "plugin")]
     fn apply(&mut self, n: Program) -> Result<Program, anyhow::Error> {
         use anyhow::Context;
+
         if self.plugins.is_none() || self.plugins.as_ref().unwrap().is_empty() {
             return Ok(n);
         }
 
         let filename = self.metadata_context.filename.clone();
 
-        if cfg!(feature = "manual-tokio-runtime") {
-            self.apply_inner(n)
-        } else {
+        #[cfg(feature = "manual-tokio-runtime")]
+        let ret = self
+            .apply_inner(n)
+            .with_context(|| format!("failed to invoke plugin on '{filename:?}'"));
+
+        #[cfg(not(feature = "manual-tokio-runtime"))]
+        let ret = {
             let fut = async move { self.apply_inner(n) };
             if let Ok(handle) = tokio::runtime::Handle::try_current() {
                 handle.block_on(fut)
             } else {
                 SHARED_RUNTIME.block_on(fut)
             }
-        }
-        .with_context(|| format!("failed to invoke plugin on '{filename:?}'"))
+            .with_context(|| format!("failed to invoke plugin on '{filename:?}'"))
+        };
+
+        ret
     }
 
     #[tracing::instrument(level = "info", skip_all, name = "apply_plugins")]