Avoid import var Foundation.stderr

```
$ echo "@preconcurrency import var Foundation.stderr" | swiftly run +main-snapshot-2026-08-11 swiftc  - -o /dev/null
<stdin>:1:28: error: ambiguous name 'stderr' in module 'Foundation'
1 | @preconcurrency import var Foundation.stderr
  |                            `- error: ambiguous name 'stderr' in module 'Foundation'
2 |

Glibc.stderr:1:32: note: found this candidate
1 | nonisolated(unsafe) public var stderr: UnsafeMutablePointer<FILE>! { get }
  |                                `- note: found this candidate

/usr/include/stdio.h:151:14: note: found this candidate
149 | extern FILE *stdin;               /* Standard input stream.  */
150 | extern FILE *stdout;              /* Standard output stream.  */
151 | extern FILE *stderr;              /* Standard error output stream.  */
    |              `- note: found this candidate
152 | /* C89/C99 say they're macros.  Make them happy.  */
153 | #define stdin stdin
```

swiftlang/swift#89891

Author: kateinoigakukun

Plugins/BridgeJS/Sources/BridgeJSTool/BridgeJSTool.swift

@@ -2,7 +2,6 @@
 @preconcurrency import func Foundation.fputs
 @preconcurrency import func Foundation.open
 @preconcurrency import func Foundation.strerror
-@preconcurrency import var Foundation.stderr
 @preconcurrency import var Foundation.errno
 @preconcurrency import var Foundation.O_WRONLY
 @preconcurrency import var Foundation.O_CREAT
@@ -15,6 +14,17 @@
 @preconcurrency import class Foundation.FileManager
 @preconcurrency import class Foundation.JSONDecoder
 @preconcurrency import class Foundation.ProcessInfo
+
+#if canImport(Darwin)
+@preconcurrency import var Darwin.stderr
+#elseif canImport(Glibc)
+@preconcurrency import var Glibc.stderr
+#elseif canImport(Musl)
+@preconcurrency import var Musl.stderr
+#elseif canImport(Android)
+@preconcurrency import var Android.stderr
+#endif
+
 import SwiftParser
 import SwiftSyntax
 

Plugins/PackageToJS/Sources/PackageToJSPlugin.swift

@@ -8,7 +8,17 @@
 @preconcurrency import struct Foundation.CocoaError
 @preconcurrency import func Foundation.fputs
 @preconcurrency import func Foundation.exit
-@preconcurrency import var Foundation.stderr
+
+#if canImport(Darwin)
+@preconcurrency import var Darwin.stderr
+#elseif canImport(Glibc)
+@preconcurrency import var Glibc.stderr
+#elseif canImport(Musl)
+@preconcurrency import var Musl.stderr
+#elseif canImport(Android)
+@preconcurrency import var Android.stderr
+#endif
+
 import PackagePlugin
 
 /// The main entry point for the PackageToJS plugin.