[gcc] Add nacl to libstdc++'s list of glibc-based architectures

gcc/libstdc++-v3/configure

Index: gcc/libstdc++-v3/configure
diff --git a/gcc/libstdc++-v3/configure b/gcc/libstdc++-v3/configure
index 20803a6ead32d21b312816a30e394d0a4db9f7df..0357aca4592da2dbec853682d65d995da0cb02f2 100755
--- a/gcc/libstdc++-v3/configure
+++ b/gcc/libstdc++-v3/configure
@@ -77201,7 +77201,10 @@ _ACEOF
 	;;
     esac
     ;;
-  *-linux* | *-uclinux* | *-gnu* | *-kfreebsd*-gnu | *-knetbsd*-gnu)
+  # TODO(mseaborn): Maybe we should handle NaCl by changing NaCl's
+  # configuration name to "nacl-gnu", so that we do not need an extra
+  # case here.
+  *-linux* | *-uclinux* | *-gnu* | *-kfreebsd*-gnu | *-knetbsd*-gnu | nacl*)
 
   # All these tests are for C++; save the language and the compiler flags.
   # The CXXFLAGS thing is suspicious, but based on similar bits previously