nss build question:how to set CFLAGS and LDFLAGS

NSS-3.33

I wanted to get code coverage of nss(mainly certutil).So I tried to add '-fprofile-arcs -ftest-coverage' to CFLAGS in command.mk. While it failed, it seems it's because compiling and linking are separate. '-fprofile-arcs -ftest-coverage' also need to be added to LDFLAGS,while I didn't find it.

Can you tell me how to configure Makefile or others to get code coverage, or is there any convenient way to set CFLAGS CXXFLAGS and LDFLAGS, just like './configure CFLAGS=...'

Thanks