Install FindPFM.cmake for bencmarkConfig.cmake

[parona-source]

There is no upstream PFM cmake package config file to use, so this has to be installed for the benchmark cmake package config file to work.

Bug: https://bugs.gentoo.org/950573
See-Also: c214639

$ bash cmake_check.sh /usr/lib64/cmake/benchmark
Temporary directory: /tmp/cmake-test.8nbt
/usr/lib64/cmake/benchmark/benchmarkConfig.cmake
CMake Error at /usr/share/cmake/Modules/CMakeFindDependencyMacro.cmake:76 (find_package):
  By not providing "FindPFM.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "PFM", but
  CMake did not find one.

  Could not find a package configuration file provided by "PFM" with any of
  the following names:

    PFMConfig.cmake
    pfm-config.cmake

  Add the installation prefix of "PFM" to CMAKE_PREFIX_PATH or set "PFM_DIR"
  to a directory containing one of the above files.  If "PFM" provides a
  separate development package or SDK, be sure it has been installed.
Call Stack (most recent call first):
  /usr/lib64/cmake/benchmark/benchmarkConfig.cmake:26 (find_dependency)
  CMakeLists.txt:3 (find_package)


Failed with:
cmake_minimum_required(VERSION 3.10)
project(test)
find_package(benchmark REQUIRED CONFIG)

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[dmah42]

thanks!