fix WASI header includes

Author: zhuowei

stdlib/public/runtime/Metadata.cpp

@@ -43,7 +43,10 @@
 #else
 #include <sys/mman.h>
 #include <unistd.h>
+// WASI doesn't have dynamic linking yet
+#ifndef __wasi__
 #include <dlfcn.h>
+#endif //__wasi
 #endif
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Hashing.h"

stdlib/public/stubs/Stubs.cpp

@@ -26,7 +26,7 @@
 #define NOMINMAX
 #include <windows.h>
 #else
-#if !defined(__HAIKU__)
+#if !defined(__HAIKU__) && !defined(__wasi__)
 #include <sys/errno.h>
 #else
 #include <errno.h>
@@ -67,7 +67,7 @@ static float swift_strtof_l(const char *nptr, char **endptr, locale_t loc) {
 #define strtod_l swift_strtod_l
 #define strtof_l swift_strtof_l
 #endif
-#elif defined(__linux__)
+#elif defined(__linux__) || defined(__wasi__)
 #include <locale.h>
 #else
 #include <xlocale.h>