[build] Add -Wshadow=local to CMake build flags.

Supported since GCC 7.0.

Author: maxsharabayko

CMakeLists.txt

@@ -642,6 +642,9 @@ endif()
 # add extra warning flags for gccish compilers
 if (HAVE_COMPILER_GNU_COMPAT)
 	set (SRT_GCC_WARN "-Wall -Wextra")
+	if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0 AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+		set (SRT_GCC_WARN "${SRT_GCC_WARN} -Wshadow=local")
+	endif()
 else()
 	# cpp debugging on Windows :D
 	#set (SRT_GCC_WARN "/showIncludes")