toolchain/ghs: Fix green hills toolchain build Vela "no storage class…

… or type specifier" error

"libcxxmini/libxx_cxa_guard.cxx", line 47: error apache#77-D: this declaration has
          no storage class or type specifier
  __extension__ typedef int __guard __attribute__((mode(__DI__)));
  ^

"libcxxmini/libxx_cxa_guard.cxx", line 47: error apache#65: expected a ";"
  __extension__ typedef int __guard __attribute__((mode(__DI__)));
                ^

"libcxxmini/libxx_cxa_guard.cxx", line 64: error apache#20: identifier "__guard" is
          undefined
    int __cxa_guard_acquire(FAR __guard *g)
                                ^

"libcxxmini/libxx_cxa_guard.cxx", line 64: error apache#20: identifier "g" is
          undefined
    int __cxa_guard_acquire(FAR __guard *g)
                                         ^

"libcxxmini/libxx_cxa_guard.cxx", line 65: error apache#65: expected a ";"
    {
    ^

"libcxxmini/libxx_cxa_guard.cxx", line 93: warning apache#12-D: parsing restarts
          here after previous syntax error
  }

Signed-off-by: yanghuatao <[email protected]>

libs/libxx/libcxxmini/libxx_cxa_guard.cxx

@@ -44,7 +44,7 @@ typedef int __guard;
 // variable and the first byte contains 0 prior to initialization, and
 // 1 after.
 
-__extension__ typedef int __guard __attribute__((mode(__DI__)));
+typedef int __guard __attribute__((mode(__DI__)));
 #endif
 
 //***************************************************************************