x86 hybrid: add provides for lib:libstdc++ in x86_gcc2

* this provides parity with the gcc_x86_syslibs packages, so
  that special handling isn't required for the gcc4hybrid
  builds when a recipe depends on libstdc++ (e.g. haikuwebkit)

src/data/package_infos/x86/haiku_secondary

@@ -19,6 +19,7 @@ flags			system_package
 
 provides {
 	haiku_%HAIKU_SECONDARY_PACKAGING_ARCH% = %HAIKU_VERSION% compat>=R1~alpha1
+	lib:libstdc++_%HAIKU_SECONDARY_PACKAGING_ARCH%
 }
 
 requires {