fix SimpleAsyncIO build for fboss.

Summary:
Evidently unlike folly, headers may be present in cmake even if they are excluded from
build.

Check that we have required headers before including AsyncIO.h or IoUring.h.

Differential Revision: D24117788

fbshipit-source-id: fec359c8298a21575a8714dd2abdbd9d4dc3e5c4

folly/experimental/io/SimpleAsyncIO.cpp

@@ -16,11 +16,11 @@
 
 #include <folly/experimental/io/SimpleAsyncIO.h>
 #include <folly/String.h>
-#if __has_include(<folly/experimental/io/AsyncIO.h>)
+#if __has_include(<folly/experimental/io/AsyncIO.h>) && __has_include(<libaio.h>)
 #define AIO_SUPPORTED
 #include <folly/experimental/io/AsyncIO.h>
 #endif
-#if __has_include(<folly/experimental/io/IoUring.h>)
+#if __has_include(<folly/experimental/io/IoUring.h>) && __has_include(<liburing.h>)
 #define IOURING_SUPPORTED
 #include <folly/experimental/io/IoUring.h>
 #endif