[libbson] Mark as not supporting static yet

ports/libbson/portfile.cmake

@@ -1,4 +1,7 @@
 include(${CMAKE_TRIPLET_FILE})
+if (VCPKG_LIBRARY_LINKAGE STREQUAL static)
+    message(FATAL_ERROR "Static building not supported yet")
+endif()
 include(vcpkg_common_functions)
 set(SOURCE_PATH ${CURRENT_BUILDTREES_DIR}/src/libbson-1.4.2)