Fix nvm on SmartOS setups using 64 bits pkgsrc repository

On SmartOS setups using 64 bits pkgsrc repositories, `nvm_get_arch`
would not handle pkg_info's output properly.

This would result in nvm not being to install any node binary when
running on SmartOS setups using a 64 bits pkgsrc repository.

This change fixes this problem, and fixes the tests suite on similar
setups.

test/fast/Unit tests/nvm_get_arch

@@ -32,6 +32,8 @@ setup_mock_arch() {
     ln -sf "${MOCKS_DIR}/isainfo_${ARCH}" ./isainfo
     if [ "_$OPT" != "_no_pkg_info" ]; then
       ln -sf "${MOCKS_DIR}/pkg_info_${ARCH}" ./pkg_info
+    else
+      ln -sf "${MOCKS_DIR}/pkg_info_fail" ./pkg_info
     fi
   fi