Implement use_static_cpp flag for Linux

(cherry picked from commit b0f41909e0)

cmake/linux.cmake

@@ -14,11 +14,25 @@ function(linux_options)
         Not implemented as compiler selection is managed by CMake. Look to
         doc/cmake.rst for examples.
     ]]
+    option(GODOTCPP_USE_STATIC_CPP "Link libgcc and libstdc++ statically for better portability" ON)
 endfunction()
 
 #[===========================[ Target Generation ]===========================]
 function(linux_generate)
+    set(STATIC_CPP "$<BOOL:${GODOTCPP_USE_STATIC_CPP}>")
+
     target_compile_definitions(godot-cpp PUBLIC LINUX_ENABLED UNIX_ENABLED)
 
+    # gersemi: off
+    target_link_options(
+        godot-cpp
+        PUBLIC
+            $<${STATIC_CPP}:
+                -static-libgcc
+                -static-libstdc++
+            >
+    )
+    # gersemi: on
+
     common_compiler_flags()
 endfunction()