Merge #243: cmake: Drop Libtool's option

414bdee fixup! cmake: Build bitcoinkernel library (Hennadii Stepanov)

Pull request description:

  The `-no-undefined` is not a linker flag, rather a Libtool flag, which we do not care about.

ACKs for top commit:
  m3dwards:
    ACK 414bdee
  theuni:
    utACK 414bdee

Tree-SHA512: 672d37f48e0c40d3802602ae64fef5d080ed66e3948241eeafa9bea5179f33ba8dd5cf6597e3e0c7f71eee48eefa57df50f6af9f032dc56c7fd3ef514d797255

src/kernel/CMakeLists.txt

@@ -90,10 +90,6 @@ target_link_libraries(bitcoinkernel
   PUBLIC
     Boost::headers
 )
-target_link_options(bitcoinkernel
-  PRIVATE
-    LINKER:-no-undefined
-)
 
 # libbitcoinkernel requires default symbol visibility, explicitly
 # specify that here so that things still work even when user