Do not define BOOST_PROGRAM_OPTIONS_SOURCE in CMakeLists.txt

Author: pdimov

CMakeLists.txt

@@ -1,5 +1,4 @@
-# Generated by `boostdep --cmake program_options`
-# Copyright 2020 Peter Dimov
+# Copyright 2020, 2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
@@ -45,7 +44,8 @@ target_link_libraries(boost_program_options
 
 target_compile_definitions(boost_program_options
   PUBLIC BOOST_PROGRAM_OPTIONS_NO_LIB
-  PRIVATE BOOST_PROGRAM_OPTIONS_SOURCE
+  # Source files already define BOOST_PROGRAM_OPTIONS_SOURCE
+  # PRIVATE BOOST_PROGRAM_OPTIONS_SOURCE
 )
 
 if(BUILD_SHARED_LIBS)
@@ -59,4 +59,3 @@ if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
   add_subdirectory(test)
 
 endif()
-