Use proper escaping for variables in Makefile
Use proper escaping for variables in Makefile


Former-commit-id: 738665563656d18b5b3e3b70d0311aa95a0f2dc8
TrimBiggs/libnetwork-plugin,robbrockbank/libcalico,Symmetric/libcalico,insequent/libcalico,L-MA/libcalico,caseydavenport/libcalico,plwhite/libcalico,projectcalico/libnetwork-plugin,alexhersh/libcalico,djosborne/libcalico,TrimBiggs/libcalico,TrimBiggs/libnetwork-plugin,tomdee/libcalico,projectcalico/libcalico,tomdee/libnetwork-plugin