Modularize cmake build config

Builds/CMake/deps/Boost.cmake

@@ -0,0 +1,92 @@
+#[===================================================================[
+   NIH dep: boost
+#]===================================================================]
+
+if ((NOT DEFINED BOOST_ROOT) AND (DEFINED ENV{BOOST_ROOT}))
+  set (BOOST_ROOT $ENV{BOOST_ROOT})
+endif ()
+file (TO_CMAKE_PATH "${BOOST_ROOT}" BOOST_ROOT)
+if (WIN32 OR CYGWIN)
+  # Workaround for MSVC having two boost versions - x86 and x64 on same PC in stage folders
+  if (DEFINED BOOST_ROOT)
+    if (IS_DIRECTORY ${BOOST_ROOT}/stage64/lib)
+      set (BOOST_LIBRARYDIR ${BOOST_ROOT}/stage64/lib)
+    else ()
+      set (BOOST_LIBRARYDIR ${BOOST_ROOT}/stage/lib)
+    endif ()
+  endif ()
+endif ()
+message (STATUS "BOOST_ROOT: ${BOOST_ROOT}")
+message (STATUS "BOOST_LIBRARYDIR: ${BOOST_LIBRARYDIR}")
+
+# uncomment the following as needed to debug FindBoost issues:
+#set (Boost_DEBUG ON)
+
+#[=========================================================[
+   boost dynamic libraries don't trivially support @rpath
+   linking right now (cmake's default), so just force
+   static linking for macos, or if requested on linux by flag
+#]=========================================================]
+if (static)
+  set (Boost_USE_STATIC_LIBS ON)
+endif ()
+set (Boost_USE_MULTITHREADED ON)
+if (static AND NOT APPLE)
+  set (Boost_USE_STATIC_RUNTIME ON)
+else ()
+  set (Boost_USE_STATIC_RUNTIME OFF)
+endif ()
+find_package (Boost 1.70 REQUIRED
+  COMPONENTS
+    chrono
+    context
+    coroutine
+    date_time
+    filesystem
+    program_options
+    regex
+    serialization
+    system
+    thread)
+
+add_library (ripple_boost INTERFACE)
+add_library (Ripple::boost ALIAS ripple_boost)
+if (is_xcode)
+  target_include_directories (ripple_boost BEFORE INTERFACE ${Boost_INCLUDE_DIRS})
+  target_compile_options (ripple_boost INTERFACE --system-header-prefix="boost/")
+else ()
+  target_include_directories (ripple_boost SYSTEM BEFORE INTERFACE ${Boost_INCLUDE_DIRS})
+endif()
+
+target_link_libraries (ripple_boost
+  INTERFACE
+    Boost::boost
+    Boost::chrono
+    Boost::coroutine
+    Boost::date_time
+    Boost::filesystem
+    Boost::program_options
+    Boost::regex
+    Boost::serialization
+    Boost::system
+    Boost::thread)
+if (san)
+  if (NOT Boost_INCLUDE_DIRS AND TARGET Boost::headers)
+    get_target_property (Boost_INCLUDE_DIRS Boost::headers INTERFACE_INCLUDE_DIRECTORIES)
+  endif ()
+  message(STATUS "Adding [${Boost_INCLUDE_DIRS}] to sanitizer blacklist")
+  file (WRITE ${CMAKE_CURRENT_BINARY_DIR}/san_bl.txt "src:${Boost_INCLUDE_DIRS}/*")
+  target_compile_options (opts
+    INTERFACE
+      # ignore boost headers for sanitizing
+      -fsanitize-blacklist=${CMAKE_CURRENT_BINARY_DIR}/san_bl.txt)
+endif ()
+
+# workaround for xcode 10.2 and boost < 1.69
+# once we require Boost 1.69 or higher, this can be removed
+# see:  https://github.com/boostorg/asio/commit/43874d5
+if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" AND
+    CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 10.0.1.10010043 AND
+    Boost_VERSION LESS 106900)
+  target_compile_definitions (opts INTERFACE BOOST_ASIO_HAS_STD_STRING_VIEW)
+endif ()