The lib/libspl/include/libgen.h header file was being mistakenly
left out of the 'make dist' tarball. It just happens this doesn't
cause a build failure when creating packages because the system
libgen/h is included instead. This simply results in the following
warning due to the missing forward declaration of mkdirp().
../../lib/libzfs/libzfs_mount.c:417:3: warning: implicit declaration
of function 'mkdirp' [-Wimplicit-function-declaration]
f2cfee80e3