Use static gbench (#1837)

RMM benchmarks should statically link Google Benchmark. We saw they were linking to `libbenchmark.so` while working with rattler-build: #1836 (comment)

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Gil Forsyth (https://github.com/gforsyth)
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)

URL: #1837

CMakeLists.txt

@@ -140,7 +140,7 @@ endif()
 
 if(BUILD_BENCHMARKS AND CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
   include(${rapids-cmake-dir}/cpm/gbench.cmake)
-  rapids_cpm_gbench()
+  rapids_cpm_gbench(BUILD_STATIC)
   add_subdirectory(benchmarks)
 endif()