add FindGflags.cmake

cmake/FindGflags.cmake

+set(_gflags_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+
+find_path(Gflags_INCLUDE_PATH gflags/gflags.h)
+
+if (Gflags_STATIC)
+  if (WIN32)
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .lib ${CMAKE_FIND_LIBRARY_SUFFIXES})
+  else (WIN32)
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .a ${CMAKE_FIND_LIBRARY_SUFFIXES})
+  endif (WIN32)
+endif (Gflags_STATIC)
+find_library(Gflags_LIBRARY NAMES gflags libgflags)
+if(Gflags_INCLUDE_PATH AND Gflags_LIBRARY)
+  set(Gflags_FOUND TRUE)
+endif(Gflags_INCLUDE_PATH AND Gflags_LIBRARY)
+if(Gflags_FOUND)
+  if(NOT Gflags_FIND_QUIETLY)
+    message(STATUS "Found gflags: ${Gflags_LIBRARY}")
+  endif(NOT Gflags_FIND_QUIETLY)
+else(Gflags_FOUND)
+  if(Gflags_FIND_REQUIRED)
+    message(FATAL_ERROR "Could not find gflags library.")
+  endif(Gflags_FIND_REQUIRED)
+endif(Gflags_FOUND)
+
+set(CMAKE_FIND_LIBRARY_SUFFIXES ${_gflags_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})