Ifdef out __wasilibc_real declarations when building wasip2

Author: catamorphism

libc-bottom-half/cloudlibc/src/libc/sched/sched_yield.c

@@ -2,10 +2,13 @@
 //
 // SPDX-License-Identifier: BSD-2-Clause
 
+#ifndef __wasilibc_use_wasip2
 #include <wasi/api.h>
+#endif
 #include <errno.h>
 #include <sched.h>
 
+#ifndef __wasilibc_use_wasip2
 int sched_yield(void) {
   __wasi_errno_t error = __wasi_sched_yield();
   if (error != 0) {
@@ -14,3 +17,4 @@ int sched_yield(void) {
   }
   return 0;
 }
+#endif

libc-bottom-half/sources/__wasilibc_real.c

@@ -10,6 +10,8 @@
  * must be modified to change this file.
  */
 
+#ifndef __wasilibc_use_wasip2
+
 #include <wasi/api.h>
 #include <string.h>
 
@@ -669,3 +671,4 @@ int32_t __wasi_thread_spawn(void* start_arg) {
     return __imported_wasi_thread_spawn((int32_t) start_arg);
 }
 #endif
+#endif // __wasilibc_use_wasip2