Enable GLIBCXX_ASSERTIONS in make develop

Not sure it's very portable, but this is only the dev config

CMakeLists.txt

@@ -52,6 +52,7 @@ else()
                   -fsanitize=alignment -fsanitize=null -fsanitize=address)
     add_compile_options(${SAN_FLAGS})
     add_link_options(${SAN_FLAGS})
+    add_definitions(-D_GLIBCXX_ASSERTIONS)
     # A non-zero optimization level is desired in debug mode, but allow overriding it nonetheless
     # TODO: this overrides anything previously set... that's a bit sloppy!
     set(CMAKE_C_FLAGS_DEBUG "-g -Og -fno-omit-frame-pointer -fno-optimize-sibling-calls" CACHE STRING "" FORCE)