https://bugs.gentoo.org/972550
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -71,10 +71,6 @@ else()
     add_compile_options("$<$<COMPILE_LANGUAGE:C,CXX>:-fstack-protector-strong;--param=ssp-buffer-size=4>")

     # Avoid re-defining _FORTIFY_SOURCE, as it can cause redefinition errors in setups that use it by default (i.e., package builds)
-    if(NOT (CMAKE_C_FLAGS MATCHES "-D_FORTIFY_SOURCE" OR CMAKE_CXX_FLAGS MATCHES "-D_FORTIFY_SOURCE"))
-        # NOTE: _FORTIFY_SOURCE requires optimizations in most newer versions of glibc
-        add_compile_options("$<$<AND:$<COMPILE_LANGUAGE:C,CXX>,$<CONFIG:Release,RelWithDebInfo>>:-D_FORTIFY_SOURCE=2>")
-    endif()

     # ATL's pack list needs more than the default 1 Mib stack on windows
     if(CMAKE_SYSTEM_NAME STREQUAL "Windows")