runtime: fix SwapByteOrder.h when building for WASI

`endian.h` in the WASI SDK include root, so should use that instead as some other platforms do.

Author: MaxDesiatov

stdlib/include/llvm/Support/SwapByteOrder.h

@@ -21,7 +21,7 @@
 #include <stdlib.h>
 #endif
 
-#if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__)
+#if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__) || defined(__wasi__)
 #include <endian.h>
 #elif defined(_AIX)
 #include <sys/machine.h>