Only load absl from third party if we do not use the bundled version …

…from protobuf.

CMakeLists.txt

@@ -23,10 +23,12 @@ include_directories(src)
 add_subdirectory(third_party)
 
 # Due to packaging changes we use the combined protobuf/absl packaging if
-# available otherwise we fallback to the older protobuf method.
-# TODO: Simplify once we can require cmake 3.27 (where CONFIG is default).
+# available otherwise we fallback to the older protobuf method. TODO: Simplify
+# once we can require cmake 3.27 (where CONFIG is default).
 find_package(Protobuf QUIET CONFIG)
-if(NOT ${Protobuf_FOUND})
+if(${Protobuf_FOUND})
+ set(PROTOBUF_LOADED_AS_CONFIG)
+else()
  find_package(Protobuf REQUIRED)
  include_directories(${Protobuf_INCLUDE_DIRS})
 endif()

third_party/CMakeLists.txt

@@ -1,7 +1,9 @@
 # SPDX-License-Identifier: Apache-2.0
 
-set(ABSL_PROPAGATE_CXX_STD ON)
-add_subdirectory(abseil-cpp)
+if(NOT ${PROTOBUF_LOADED_AS_CONFIG})
+ set(ABSL_PROPAGATE_CXX_STD ON)
+ add_subdirectory(abseil-cpp)
+endif()
 
 set(BUILD_TZ_LIB ON)
 add_subdirectory(datetime)