editors/nano: Fix build (configure) on ARM

The arm package builder when building this port, fails with the following
error during configure:

checking whether printf survives out-of-memory conditions...
=>> Killing runaway build after 21600 seconds with no output

The root cause is described in bug 224740, which has not been resolved yet:

low RLIMIT_VMEM hangs qemu due to GSlice allocation failure

In the meantime, this change applies a known workaround which has already
been applied in several ports, which disables the specific (hanging) configure
check, if the build is run with qemu emulation.

PR: 231346, 224740
Reported by: many
Approved by: portmgr (blanket: build fix, jfi)
MFH: 2018Q4