configure warning suggests an anti-pattern

[Bruno Haible]

On a Linux/mips machine, I'm compiling 32-bit binaries by setting

  CC="gcc -mabi=32"
  CXX="g++ -mabi=32"

This is the recommended way to do, per the Autoconf manual
<https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.70/html_node/Preset-Output-Variables.html>
Quote:

  "If an option selects a 32-bit or 64-bit build on a bi-arch system,
   it must be put direcly into CC, e.g., CC='gcc -m64'. This is necessary
   for config.guess to work right."

Now the configuration of GNU ncurses 6.2 gives me a warning:

$ ./configure
...
checking for gcc -mabi=32 option to accept ANSI C... none needed
checking $CFLAGS variable... ok
checking $CC variable... broken
configure: WARNING: your environment uses the CC variable to hold 
CFLAGS/CPPFLAGS options
...

There is nothing to warn about! Putting '-mabi=32' into CFLAGS or CPPFLAGS
would be an anti-pattern, because it would break 'config.guess'.

Bruno