[BUG] Fix compiler warning on OS X

[qu1j0t3]

Noticed this warning.

Fixed by this change: qu1j0t3@eabe681

Opened an issue according to guideline in Contributing.txt

Describe the bug
Compiler warning on OS X.

To Reproduce
Steps to reproduce the behavior:

1. make
2. Warning shown:

$ make
Building library: library/micronucleus_lib.c...
gcc -I/usr/local/Cellar/libusb/1.0.26/include/libusb-1.0 -I/usr/local/Cellar/libusb-compat/0.1.8/include -Ilibrary -O -g -D MAC_OS -D MAC_OS_PKGCONFIG -c library/micronucleus_lib.c
library/micronucleus_lib.c:301:16: warning: passing 'unsigned char [page_length]' to parameter of type 'char *' converts
      between pointers to integer types with different sign [-Wpointer-sign]
               page_buffer, page_length,
               ^~~~~~~~~~~
/usr/local/Cellar/libusb-compat/0.1.8/include/usb.h:330:30: note: passing argument to parameter 'bytes' here
        int value, int index, char *bytes, int size, int timeout);
                                    ^
1 warning generated.

Expected behavior
Clean compile.

Used Hardware
n/a

Desktop (please complete the following information):

• OS: OS X 10.15.7