Add missing headers (#15075)

Some systems must explicitly include these headers.

Utilities/JITASM.cpp

@@ -10,6 +10,7 @@
 #include "util/simd.hpp"
 
 #ifdef __linux__
+#include <unistd.h>
 #define CAN_OVERCOMMIT
 #endif
 

Utilities/Thread.cpp

@@ -46,6 +46,7 @@ DYNAMIC_IMPORT_RENAME("Kernel32.dll", SetThreadDescriptionImport, "SetThreadDesc
 #include <time.h>
 #endif
 #ifdef __linux__
+#include <sys/syscall.h>
 #include <sys/timerfd.h>
 #include <unistd.h>
 #endif