Ensure that the choice of compiler and target is passed to sub-projects. (#17732)

If not explicitly set using exported environment variables, the choice
of compilers and compiler targets used by CMake does not get propagated
to sub-porjects created with ExternalProject_Add or
FetchContent_Declare.

In most cases this does not matter, because very few people are building
using non-default compilers for their environment, but it can cause
issues in two specific cases:

- If building for the same system that the build is happening on, but
  using a non-default compiler specified using CMake arguments (instead
  of via exported environment variables), sub-projects will still use
  the default compiler for the system, which may result in linking
  errors (or runtime failures even if the link succeeds).
- If cross-compiling and not using the preferred approaches of either a
  toolchain file or exported environment variables, sub-projects may not
  even build for the correct CPU architecture, causing the build to
  fail.

This adds logic to ensure that the compiler and compiler targets get
propagated correctly even if they are just specified on the command
line, thus avoiding the above two possibilities.

1 files changed, 2 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a0c30570c8..65fdd3bdcf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -204,6 +204,7 @@ endif()
 
 if(ENABLE_WEBRTC)
         include(FetchContent)
+        include(NetdataFetchContentExtra)
 
         # ignore debhelper
         set(FETCHCONTENT_FULLY_DISCONNECTED Off)
@@ -217,6 +218,7 @@ if(ENABLE_WEBRTC)
         FetchContent_Declare(libdatachannel
             GIT_REPOSITORY https://github.com/paullouisageneau/libdatachannel.git
             GIT_TAG v0.20.1
+            CMAKE_ARGS ${NETDATA_PROPAGATE_TOOLCHAIN_ARGS}
         )
         FetchContent_MakeAvailable(libdatachannel)
 endif()