Append to GNU make variables via command line

Question

I am using a GNU-make Makefile to build a C project with several targets (all, clean, and a few project specific targets). In the process of debugg

Answer 1

For the record, @Carl Norum's answer prepends the variable, from the command line perspective.

I needed a way to actually append and came up with:

override CFLAGS := -Wall $(CFLAGS)