small changes which allows to work with old git (got rid of "git -C")

cmake/compileenv.txt

@@ -8,13 +8,13 @@ string(TIMESTAMP compile_time)
 set(git_hash unkown)
 
 if (EXISTS ${CMAKE_SOURCE_DIR}/.git)
-  execute_process(COMMAND git -C ${CMAKE_SOURCE_DIR} describe --tags OUTPUT_VARIABLE git_describe)
+  execute_process(COMMAND git describe --tags WORKING_DIRECTORY ${CMAKE_SOURCE_DIR} OUTPUT_VARIABLE git_describe)
   if (${git_describe})
 	message("GIT DESCRIBE:${git_describe}")
   else()
      set(git_describe unkown)
   endif()
-  execute_process(COMMAND git -C ${CMAKE_SOURCE_DIR} rev-parse  HEAD OUTPUT_VARIABLE git_hash)
+  execute_process(COMMAND git rev-parse  HEAD WORKING_DIRECTORY ${CMAKE_SOURCE_DIR} OUTPUT_VARIABLE git_hash)
 elseif (EXISTS ${CMAKE_SOURCE_DIR}/version)
   file(READ ${CMAKE_SOURCE_DIR}/version git_describe)
 else()