Helmut Grohne authored Jul 18, 2018 and Kevin Brace committed Jul 18, 2018

configure.ac fails to cross build from source, because it abuses
AC_CHECK_FILE for finding headers. AC_CHECK_FILE is supposed to find
files on the host system. You cannot usually expect the host system
to have headers, so this use is incorrect. It happens to also break
cross compilation.

Signed-off-by: Helmut Grohne <helmut@subdivi.de>