bug#6538: Removal of C_DEBUG_SWITCH changes CFLAGS

[Dan Nicolaescu]

Glenn Morris <rgm@gnu.org> writes:

> Package: emacs
>
> Configuring Emacs 23.2 on Solaris 2.10 with a non-GNU cc, one gets
> generated Makefiles containing:
>
> CFLAGS=-g -O 
>
> Configuring the current trunk, one gets
>
> CFLAGS=
>
> The cause appears to be the removal of C_DEBUG_SWITCH.

> It is possible other platforms are affected, I did not check (likewise
> with LIBS_DEBUG).

LIBS_DEBUG was just -lg, it can be safely ignored.

>
> The configure logic (faithfully inherited from cpp) is weird. Eg
> C_OPTIMIZE_SWITCH goes unused with non-GNU compilers.

Not anymore.  
C_DEBUG_SWITCH was weird, it used to specify optimization flags too,
that's probably why C_OPTIMIZE_SWITCH is unused.
C_DEBUG_SWITCH was just -g -O for all platforms that bothered to set it.  
We get that anyway for non-GCC compilers.