What is being reported as an error is something I thought was fixed some time ago, so can you check you have the latest version of FontBuilder and the library files?
Basically the problem is that in C++ is a line ends with '\' the compiler thinks that it continues on the next line.
Looks for a line that looks like this in the font .h file (in the libraries/MD_Parola folder)
5, 2, 4, 8, 16, 32, // 92 - \
and change it to this
5, 2, 4, 8, 16, 32, // 92 - '\'
By putting the character in single quotes it changes the special meaning of the character at the end of the line.