libphobos: Fix assert in core.sys.posix.sys.stat for aarch64/ilp32.

Merges upstream druntime 51365217.

Reviewed-on: https://github.com/dlang/druntime/pull/2579

From-SVN: r270541

libphobos/libdruntime/MERGE

-b43203a134fb5e259ffc1711cc061c6e869b56f6
+513652173d6f02206be3ddaa2b6ed0b191ea4e3d
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/druntime repository.

libphobos/libdruntime/core/sys/posix/sys/stat.d

@@ -709,10 +709,10 @@ version (CRuntime_Glibc)
             }
             int[2] __unused;
         }
-        static if (__USE_FILE_OFFSET64)
+        version (D_LP64)
             static assert(stat_t.sizeof == 128);
         else
-            static assert(stat_t.sizeof == 128);
+            static assert(stat_t.sizeof == 104);
     }
     else version (SPARC64)
     {