CMake find_package file to find Google Benchmark. Just sets up targets, does not download. Only tested on Linux.

FindGBench.cmake

#Copyright 2022 Bryan J. Lunt <[email protected]>
#
#Licensed under the Apache License, Version 2.0 (the "License");
#you may not use this file except in compliance with the License.
#You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
#Unless required by applicable law or agreed to in writing, software
#distributed under the License is distributed on an "AS IS" BASIS,
#WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#See the License for the specific language governing permissions and
#limitations under the License.

### Version 4 of this cmake file ###

find_path(GBENCH_INCLUDE_DIR "benchmark/benchmark.h"
	HINTS ${GBENCH_ROOT}/include
	$ENV{GBENCH_ROOT}/include
)
mark_as_advanced(GBENCH_INCLUDE_DIR)

find_library(GBENCH_LIBRARY "${CMAKE_STATIC_LIBRARY_PREFIX}benchmark${CMAKE_STATIC_LIBRARY_SUFFIX}")
find_library(GBENCH_MAIN_LIBRARY "${CMAKE_STATIC_LIBRARY_PREFIX}benchmark_main${CMAKE_STATIC_LIBRARY_SUFFIX}")

#find_library(GBENCH_CORE_LIBRARIES_SHARED "${CMAKE_SHARED_LIBRARY_PREFIX}benchmark${CMAKE_SHARED_LIBRARY_SUFFIX}")
#find_library(GBENCH_MAIN_LIBRARIES_SHARED "${CMAKE_SHARED_LIBRARY_PREFIX}benchmark_main${CMAKE_SHARED_LIBRARY_SUFFIX}")


#mark_as_advanced(GBENCH_INCLUDE_DIR)

#
#Google Test uses names (CMake 3.22): GTest::gtest GTest::gtest_main
#and 					(CMake 3.12): GTest::GTest GTest::Main
#follow that precedent.
#

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(GBench DEFAULT_MSG GBENCH_LIBRARY GBENCH_INCLUDE_DIR GBENCH_MAIN_LIBRARY)


if(GBENCH_FOUND)
	#set(GBENCH_FOUND "TRUE")
	set(GBENCH_BOTH_LIBRARIES ${GBENCH_LIBRARY} ${GBENCH_MAIN_LIBRARY})
	set(GBENCH_INCLUDE_DIRS ${GBENCH_INCLUDE_DIR})
	#message("GBENCH: ${GBENCH_LIBRARY} ${GBENCH_LIBRARY_MAIN}")
	
	find_package(Threads QUIET REQUIRED)
	
	if(NOT TARGET GBench::gbench)
		add_library(GBench::gbench STATIC IMPORTED )
		set_target_properties(GBench::gbench PROPERTIES IMPORTED_LOCATION ${GBENCH_LIBRARY})
		target_link_libraries(GBench::gbench INTERFACE ${GBENCH_LIBRARY})
		target_include_directories(GBench::gbench INTERFACE ${GBENCH_INCLUDE_DIRS})
		
		if(TARGET Threads::Threads)
			target_link_libraries(GBench::gbench INTERFACE Threads::Threads)
		endif()
	endif()
	
	if(NOT TARGET GBench::gbench_main)
		add_library(GBench::gbench_main STATIC IMPORTED )
		set_target_properties(GBench::gbench_main PROPERTIES IMPORTED_LOCATION ${GBENCH_MAIN_LIBRARY})
		target_link_libraries(GBench::gbench_main INTERFACE GBench::gbench)
		target_link_libraries(GBench::gbench_main INTERFACE ${GBENCH_MAIN_LIBRARY})
		target_include_directories(GBench::gbench_main INTERFACE ${GBENCH_INCLUDE_DIRS})
	endif()
	
	#add_library(GoogleBenchmark INTERFACE)
	#target_link_libraries(GoogleBenchmark INTERFACE GBench::gbench)
	#TODO: Make linking (and even finding) main optional.
	#target_link_libraries(GoogleBenchmark INTERFACE GBench::gbench_main)
	
endif()

Finding the Threads package is REQUIRED, so maybe it would be more defensive to make the linkage to GBench::gbench (L57) unconditional. It would be better to have CMake die with a clear reason than to get a linker error later.