Update CMakeLists

- remove GOLD linker special case handling
- bump minimum cmake version to 3.20
- simplify LTO detection
- remove outdated way to check for compiler flags
- remove outdated compiler version gates (rely on CXX version)
- remove outdated Apple platform handling
- disable compiler-specific CXX extensions
- require boost 1.70 in all builds
- remove unused variable

src/nodejs/CMakeLists.txt

@@ -1,6 +1,4 @@
-# node-cmake requires CMake 3.1 features; for the osrm project we only
-# require CMake 2.8.11 so that we can build e.g. on Trusty by default.
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.20)
 
 message(STATUS "Building node_osrm")