[WASM] Export WASILibc

Author: kateinoigakukun

Sources/Foundation/NSSwiftRuntime.swift

@@ -14,8 +14,10 @@
 // This mimics the behavior of the swift sdk overlay on Darwin
 #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
 @_exported import Darwin
-#elseif os(Linux) || os(Android) || CYGWIN || os(WASI)
+#elseif os(Linux) || os(Android) || CYGWIN
 @_exported import Glibc
+#elseif os(WASI)
+@_exported import WASILibc
 #elseif os(Windows)
 @_exported import MSVCRT
 #endif