gcc-plugins: fix gcc 11 indigestion with plugins...

Fedora Rawhide has started including gcc 11,and the g++ compiler throws a wobbly when it hits scripts/gcc-plugins:

HOSTCXX scripts/gcc-plugins/latent_entropy_plugin.so In file included from /usr/include/c++/11/type_traits:35, from /usr/lib/gcc/x86_64-redhat-linux/11/plugin/include/system.h:244, from /usr/lib/gcc/x86_64-redhat-linux/11/plugin/include/gcc-plugin.h:28, from scripts/gcc-plugins/gcc-common.h:7, from scripts/gcc-plugins/latent_entropy_plugin.c:78: /usr/include/c++/11/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options. 32 | #error This file requires compiler and library support \

In fact, it works just fine with c++11, which has been in gcc since 4.8, and we now require 4.9 as a minimum.

Signed-off-by: Valdis Kletnieks valdis.kletnieks@vt.edu