- pass compilation flags

--- CMakeLists.txt.orig	2022-07-09 18:30:09 UTC
+++ CMakeLists.txt
@@ -248,7 +248,7 @@ endif()
 if(WIN32)
   set(CMAKE_CXX_FLAGS "-Wall -std=c++0x -fpermissive -U__STRICT_ANSI__")
 else()
-  set(CMAKE_CXX_FLAGS "-Wall -std=c++11")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -std=c++11")
 endif()
 
 # indiscriminate copy/paste from: