Pragma's names are case sensitive, inline and INLINE is not the same. And in the answer above, I meant to mention that there is a pragma INLINE, I noticed I typed INTERRUPT instead.
Use (I did not try this out)
#pragma INLINE
// Read the content of a memory address
char flash_read(unsigned int address)
{
const char *pointer;
pointer = (const char*) address;
return (*pointer);
}