Disable GCC optimization that prevents mod dlls from unloading after …

…engine calls dlclose

linux/Makefile

@@ -43,9 +43,12 @@ BASE_CFLAGS=-std=c++17 -fpermissive -fno-strict-aliasing -fno-exceptions -fexpen
 BASE_CFLAGS+=-DNDEBUG -DPOSIX -D_POSIX -DLINUX -D_LINUX -DGNUC -DNO_MALLOC_OVERRIDE -DCLIENT_WEAPONS
 
 # flifetime-dse=1 is needed to disable a compiler optimization that optimizes out std::memset calls in CBaseEntity::operator new
-# See https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flifetime-dse for more information about the flifetime-dse flag
+# See https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flifetime-dse for more information about this flag
+# fno-gnu-unique is needed to disable a compiler optimization that prevents dlclose from unloading mod dlls,
+# causing them to retain state and crash when the engine tries to access memory in an invalid way
+# See https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#index-fno-gnu-unique for more informatio about this flag
 ifeq "$(COMPILER)" "g++"
-	BASE_CFLAGS+=-flifetime-dse=1
+	BASE_CFLAGS+=-flifetime-dse=1 -fno-gnu-unique
 endif
 
 SHLIBEXT=so