libretro-mupen64plus: fix build w/ gcc10

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

@@ -0,0 +1,10 @@
+--- GLideN64/src/ShaderUtils.h	2019-05-31 19:25:22.000000000 +0200
++++ GLideN64/src/ShaderUtils.h	2020-09-24 17:12:36.260736024 +0200
+@@ -3,6 +3,7 @@
+ 
+ #include "OpenGL.h"
+ #include "Combiner.h"
++#include <string>
+ 
+ GLuint createShaderProgram(const char * _strVertex, const char * _strFragment);
+ bool checkShaderCompileStatus(GLuint obj);

srcpkgs/libretro-mupen64plus/template

@@ -24,6 +24,8 @@ case "$XBPS_TARGET_MACHINE" in
 	armv*|aarch64*) build_options_default="gles";;
 esac
 
+CFLAGS="-fcommon"
+
 do_build() {
 	local _args