LibC: Compile with -O2 optimizations

I have no idea why libc had no optimizations enabled.

Weird thing is that memcpy optimized to infinite loop if I kept the
__restrict__ attributes in pointers. I don't think there was any ub.

libc/string.cpp

@@ -17,7 +17,7 @@ int memcmp(const void* s1, const void* s2, size_t n)
 	return 0;
 }
 
-void* memcpy(void* __restrict__ dstp, const void* __restrict__ srcp, size_t n)
+void* memcpy(void* dstp, const void* srcp, size_t n)
 {
 	unsigned char* dst = static_cast<unsigned char*>(dstp);
 	const unsigned char* src = static_cast<const unsigned char*>(srcp);