fix finding runtime files relative to the executable path

src/core/Runtime.cc

@@ -6,9 +6,9 @@ static const std::initializer_list<const char *> Shader_Extensions = {"", ".glsl
 
 static std::string System_Runtime_Dir;
 
-void Runtime::init(const char * argv_0, const char * appname)
+void Runtime::init(const char * executable_path, const char * appname)
 {
-    System_Runtime_Dir = Path::join(Path::dirname(Path::dirname(argv_0)), "share", appname);
+    System_Runtime_Dir = Path::join(Path::dirname(Path::dirname(executable_path)), "share", appname);
 }
 
 std::string Runtime::find(Type t, const std::string & name)

src/core/Runtime.h

@@ -14,7 +14,7 @@ public:
     };
 
     static std::string find(Type t, const std::string & name);
-    static void init(const char * argv_0, const char * appname);
+    static void init(const char * executable_path, const char * appname);
 
 protected:
     static std::string find_first_under(const std::string & runtime_subpath,