To be investigated: restore cxa_pure_virtual

Looks like it's very hard to remove it for good (will be generated by a lot of patterns and the gcc flags are not enough)

Author: facchinm

cores/arduino/abi.cpp

@@ -6,6 +6,8 @@
 
 #include "new.h"
 
+extern "C" void __cxa_pure_virtual() {}
+
 // The C++ spec dictates that allocation failure should cause the
 // (non-nothrow version of the) operator new to throw an exception.
 // Since we expect to have exceptions disabled, it would be more