Setting optimizations without violating autotools principles

[Chris Stankevitz]

Q1: How do I specify that I want optimizations turned off?
a) in Makefile.am: AM_CFLAGS = -O0
b) in configure.ac: CFLAGS="$CFLAGS -O0"
c) other

Q2: Does your answer for Q1 work even when I use AC_PROG_CC which places -02 in 
CFLAGS?

Q3: Does your answer for Q1 violate this autotools principle:
You should never redefine a user variable such as CFLAGS 
(http://tinyurl.com/3wkfdp5)

Q4: Does AC_PROG_CC violate this principle?

Thank you,

Chris