fix cmake xxhash discovery

Summary:
Fix fb303 OSS builds on macOS that failing to find xxhash.h.

Problem was that thrift cpp lib now needs xxhash but it wasn't declared in the cmake rules, which shows up as a problem when system xxhash is not installed.

CustomCompressorRegistry.cpp was also missing from cmake build resulting in link errors once the xxhash.h discovery was fixed.

Reviewed By: markbt

Differential Revision: D72452460

fbshipit-source-id: 6bdb8e0e3961529f04f9d9d29ba0daeff2e7ff2a

Author: ahornby

build/fbcode_builder/CMake/FBThriftCppLibrary.cmake

@@ -144,6 +144,7 @@ function(add_fbthrift_cpp_library LIB_NAME THRIFT_FILE)
     PUBLIC
       "$<BUILD_INTERFACE:${CMAKE_BINARY_DIR}>"
       "$<INSTALL_INTERFACE:${ARG_INCLUDE_DIR}>"
+      ${Xxhash_INCLUDE_DIR}
   )
   target_link_libraries(
     "${LIB_NAME}"
@@ -153,6 +154,7 @@ function(add_fbthrift_cpp_library LIB_NAME THRIFT_FILE)
       Folly::folly
       mvfst::mvfst_server_async_tran
       mvfst::mvfst_server
+      ${Xxhash_LIBRARY}
   )
 
   # Add ${generated_headers} to the PUBLIC_HEADER property for ${LIB_NAME}