core: declare initVariant() as weak

Signed-off-by: Aymane Bahssain <aymane.bahssain@st.com>

Author: Aymane-ST

api/Common.h

@@ -98,7 +98,7 @@ typedef uint8_t   byte;
 typedef uint16_t  word;
 
 void init(void);
-void initVariant(void);
+void initVariant(void) __attribute__((weak));
 
 #ifndef HOST
 int atexit(void (*func)()) __attribute__((weak));