Add boost headers

Recent versions of boost-di require boost headers as a transitive
dependency. Since those are included via FindPackage we need to
override its default behavior so our target pulled in via
FetchContent can be found instead of some system version.

vmicore/src/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.16)
+cmake_minimum_required(VERSION 3.24)
 project(vmicore)
 
 include(CheckPIESupported)
@@ -17,6 +17,13 @@ target_link_libraries(vmicore vmicore-lib)
 
 # Setup Boost DI
 
+FetchContent_Declare(
+        Boost
+        GIT_REPOSITORY https://github.com/boostorg/headers
+        GIT_TAG master
+        OVERRIDE_FIND_PACKAGE
+)
+
 FetchContent_Declare(
         boost-di
         GIT_REPOSITORY https://github.com/boost-ext/di.git