libretro-mupen64plus-rpi: fix build

srcpkgs/libretro-mupen64plus-rpi/patches/string.patch

@@ -0,0 +1,10 @@
+--- GLideN64/src/ShaderUtils.h	2019-05-31 19:25:22.000000000 +0200
++++ GLideN64/src/ShaderUtils.h	2021-03-02 14:30:43.395732704 +0100
+@@ -1,6 +1,7 @@
+ #ifndef SHADER_UTILS_H
+ #define SHADER_UTILS_H
+ 
++#include <string>
+ #include "OpenGL.h"
+ #include "Combiner.h"
+ 

srcpkgs/libretro-mupen64plus-rpi/template

@@ -15,6 +15,8 @@ distfiles="https://github.com/libretro/mupen64plus-libretro/archive/${_gitrev}.t
 checksum=947abfb1d5ff34d6b22fecfb2df02bd3759fde3f4a0e5d238f65ec7e97d964d4
 conflicts="ĺibretro-mupen64plus>=0"
 
+CFLAGS="-fcommon"
+
 do_build() {
 	local _args="ARCH=arm"