Merge #133: Fix debian "libatomic not found" error in downstream builds

67afc23 Fix debian "libatomic not found" error in downstream builds (Ryan Ofsky)

Pull request description:

  This is an extension of the workaround implemented previously in #119. That workaround let the libmultiprocess cmake build work with the debian capnproto package.

  This change extends the workaround to apply to downstream cmake builds that call find_package(Libmultiprocess), like Bitcoin Core.

  Fixes #132

ACKs for top commit:
  hebasto:
    ACK 67afc23, tested on Ubuntu 24.04.

Tree-SHA512: 9b02f9f4d9aea3ac241641fe857dd91e110252c93351ed2fdd0bcd48f3dbfea3b3d5476774a2d4b89a70c955a7c7fc69eaba6f0a41e853e2eb03d3dae6ad3c8e

Author: ryanofsky

cmake/Config.cmake.in

@@ -17,6 +17,9 @@ if ("Bin" IN_LIST ${CMAKE_FIND_PACKAGE_NAME}_FIND_COMPONENTS)
 endif()
 
 if ("Lib" IN_LIST ${CMAKE_FIND_PACKAGE_NAME}_FIND_COMPONENTS)
+  # Setting FOUND_LIBATOMIC is needed on debian & ubuntu systems to work around bug in
+  # their capnproto packages. See compat_find.cmake for a more complete explanation.
+  set(FOUND_LIBATOMIC TRUE)
   include(CMakeFindDependencyMacro)
   find_dependency(CapnProto)
 endif()