Fix build with Boost 1.89.0

[cho-m]

In the upcoming Boost 1.89.0 release, the Boost.System stub library introduced back in 1.69¹ has been removed (boostorg/system@7a495bb), which causes a CMake error when system component is required.

This PR change using OPTIONAL_COMPONENTS is based on upstream comment https://github.com/boostorg/system/issues/132#issuecomment-3146378680 given that Boost 1.62 is still supported.

If minimum is increased to 1.69 (or later), then can remove system instead, e.g.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e19d18f1b..8f0b6fbab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,10 +41,9 @@ fb_activate_static_library_option()
 set(QUIC_FBCODE_ROOT ${CMAKE_CURRENT_SOURCE_DIR})
 
 # Dependencies
-find_package(Boost 1.62
+find_package(Boost 1.69
   REQUIRED COMPONENTS
   iostreams
-  system
   thread
   filesystem
   regex

Footnotes

1. https://www.boost.org/doc/libs/1_69_0/libs/system/doc/html/system.html#changes_in_boost_1_69 ↩

[cho-m]

mvfst/CMakeLists.txt

Line 6 in 3603e7f

cmake_minimum_required(VERSION 3.10)

CMake 3.11 introduced OPTIONAL_COMPONENTS but project allows 3.10 so will need some more work.

Easiest options are increasing CMake to 3.11 or increasing Boost to 1.69. Otherwise, may have to run find_package twice.