[FIXUP] for "cmake: Build test_bitcoin executable"

The vcpkg package manager has a separated `boost-test` package, and it
is more robust to test its headers explicitly.

cmake/module/AddBoostIfNeeded.cmake

@@ -28,5 +28,28 @@ function(add_boost_if_needed)
     add_library(Boost::headers ALIAS Boost::boost)
   endif()
 
+  if(BUILD_TESTS)
+    include(CheckCXXSourceCompiles)
+    set(CMAKE_REQUIRED_INCLUDES ${Boost_INCLUDE_DIR})
+    check_cxx_source_compiles("
+      #define BOOST_TEST_MAIN
+      #include <boost/test/included/unit_test.hpp>
+      " HAVE_BOOST_INCLUDED_UNIT_TEST_H
+    )
+    if(NOT HAVE_BOOST_INCLUDED_UNIT_TEST_H)
+      message(FATAL_ERROR "Building test_bitcoin executable requested but boost/test/included/unit_test.hpp header not available.")
+    endif()
+
+    check_cxx_source_compiles("
+      #define BOOST_TEST_MAIN
+      #include <boost/test/included/unit_test.hpp>
+      #include <boost/test/unit_test.hpp>
+      " HAVE_BOOST_UNIT_TEST_H
+    )
+    if(NOT HAVE_BOOST_UNIT_TEST_H)
+      message(FATAL_ERROR "Building test_bitcoin executable requested but boost/test/unit_test.hpp header not available.")
+    endif()
+  endif()
+
   mark_as_advanced(Boost_INCLUDE_DIR)
 endfunction()