Update envcov.sh
Update envcov.sh

Fix a bug that env.sh was not found when you call ``getcov`` form outside the XcodeCoverage folder
DoubleNode/XcodeCoverage,designatednerd/XcodeCoverage,Hibbert-pku/XcodeCoverage,vokal/XcodeCoverage,DoubleNode/XcodeCoverage,designatednerd/XcodeCoverage,zendesk/XcodeCoverage,zendesk/XcodeCoverage,vokal/XcodeCoverage,Hibbert-pku/XcodeCoverage,DoubleNode/XcodeCoverage,vokal/XcodeCoverage,scottrasche/XcodeCoverage,scottrasche/XcodeCoverage,designatednerd/XcodeCoverage,vokal/XcodeCoverage,Hibbert-pku/XcodeCoverage,designatednerd/XcodeCoverage,zendesk/XcodeCoverage,zendesk/XcodeCoverage,scottrasche/XcodeCoverage,Hibbert-pku/XcodeCoverage,scottrasche/XcodeCoverage,DoubleNode/XcodeCoverage