poison: remove GNUC check

QEMU requires Clang or GCC, that define and support __GNUC__ extensions

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20201210134752.780923-10-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/poison.h

@@ -3,7 +3,6 @@
 
 #ifndef HW_POISON_H
 #define HW_POISON_H
-#ifdef __GNUC__
 
 #pragma GCC poison TARGET_I386
 #pragma GCC poison TARGET_X86_64
@@ -93,4 +92,3 @@
 #pragma GCC poison CONFIG_SOFTMMU
 
 #endif
-#endif