export PKG_CONFIG_PATH

export PKG_CONFIG_PATH for qnx compile, I'm not sure why we have to change this, but compiling on QNX failed from some point, that breaks http://jenkins.jsk.imi.i.u-tokyo.ac.jp:8080/job/hrpsys-qnx/1555/console, as reported on https://github.com/fkanehiro/hrpsys-base/pull/287#issuecomment-51409844

Currently, we're testing with previous version at  http://jenkins.jsk.imi.i.u-tokyo.ac.jp:8080/job/qnx-hrpsys-build/15/console and hope this failed, and next compile on qnx-hrpsys-build will pass the test.