Scope compiler warning flags to project source and add stricter checks

Signed-off-by: Javier Balloffet <javier.balloffet@gmail.com>

Author: jballoffet

andino_firmware/platformio.ini

@@ -15,9 +15,15 @@ default_envs = uno, nanoatmega328
 [base_build]
 build_flags =
   -I include
+build_src_flags =
   -Wall -Wextra
   -Wshadow
   -Wdouble-promotion
+  -Woverloaded-virtual
+  -Wcast-qual
+  -Wuseless-cast
+  -Wnull-dereference
+  -Werror
 check_tool = cppcheck
 check_skip_packages = yes
 check_flags =