Workaround build failure on -fno-common toolchains like upstream
gcc-10. Otherwise build fails as:
ld: ../ipsw-patch/libxpwn.a(libxpwn.c.o):(.bss+0x4): multiple definition of
`endianness'; CMakeFiles/xpwn-bin.dir/src/xpwn.cpp.o:(.bss+0x0): first defined here