devel/libunistring: temporarily skip ENOMEM check for printf

configure:25883: checking whether printf survives out-of-memory conditions
configure:26055: /nxb-bin/usr/bin/cc -o conftest -O2 -pipe -DLIBICONV_PLUG -fno-strict-aliasing -DLIBICONV_PLUG -D_THREAD_SAFE conftest.c >&5
configure:26058: $? = 0

*MEMORY-ERROR*: [67280]: GSlice: failed to allocate 496 bytes (alignment: 512): Cannot allocate memory

PR: 224740
Reported by: Mark Millard (via ports@ list, for armv7)
Approved by: portmgr blanket