INTERPROCEDURAL_OPTIMIZATION for GCC

Based on the Nils Gladitz patch.

Related issues:

• #16665 (closed)
• #15939 (closed)
• #15245 (closed)

Tested on Linux (GCC and GCC Android) with example:

cmake_minimum_required(VERSION 3.7)
project(foo)

add_library(a STATIC a.cpp)

add_executable(b main.cpp)
target_link_libraries(b PUBLIC a)

add_library(c SHARED main.cpp)
target_link_libraries(c PUBLIC a)

set_target_properties(a b c PROPERTIES INTERPROCEDURAL_OPTIMIZATION TRUE)