Install FindPFM.cmake for bencmarkConfig.cmake

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
Signed-off-by: Alfred Wingate <parona@protonmail.com>

Author: parona-source

cmake/Config.cmake.in

@@ -5,6 +5,7 @@ include (CMakeFindDependencyMacro)
 find_dependency (Threads)
 
 if (@BENCHMARK_ENABLE_LIBPFM@)
+    list(PREPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
     find_dependency (PFM)
 endif()
 

src/CMakeLists.txt

@@ -39,6 +39,9 @@ set_property(
 if (PFM_FOUND)
   target_link_libraries(benchmark PRIVATE PFM::libpfm)
   target_compile_definitions(benchmark PRIVATE -DHAVE_LIBPFM)
+  install(
+      FILES "${PROJECT_SOURCE_DIR}/cmake/Modules/FindPFM.cmake"
+      DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 endif()
 
 # pthread affinity, if available