Honor environment variables CFLAGS, CPPFLAGS, and LDFLAGS

[rlaboiss]

The building of the zmat package ignores the setting of the environment variables CFLAGS, CPPFLAGS, and LDFLAGS.

We are currently applying a patch to the Debian package zmat that fixes the problem. This allows the inclusion of hardening flags like -D_FORTIFY_SOURCE=2, -fstack-protector-strong, -Wformat, -Werror=format-security, and -Wl,-z,relro.

[fangq]

hi Rafael, so glad to hear from you. yes, I meant to back port those patches for the next release, thanks for reminding, should be fixed now.