fix(freelist): add missing stdbool.h include

C99 does not define bool as a keyword (unlike C11 and beyond), which
means that files are free to use `bool` as something other than a type
name. When <stdbool.h> is not included through some other mechanism,
-Wc++-compat treats it as such and complains that it's a reserved
keyword in C++.

freelist.h uses bool, but does not bring in stdbool.h; add <stdbool.h>

Signed-off-by: Nicholas Sielicki <nslick@amazon.com>

include/nccl_ofi_freelist.h

@@ -10,6 +10,7 @@
 extern "C" {
 #endif
 
+#include <stdbool.h>
 #include <assert.h>
 #include <stdlib.h>
 #include <pthread.h>