Help with -Werror

[Phillip Susi]

It seems like every time I go back to try to do somoe work on the parted
sources I run into a failure to compile due to some silly warning or
other and -Werror being enabled.  This time it is from a generated
source file made by gperf.  Is this set by default these days in
automake?  Because I can not figure out how it is being used.
Makefile.am does not seem to have anything to turn it on.  Makefile sets
CFLAGS_WERROR=-Werror, but I can see nothing that references
CFLAGS_WERROR anywhere.  How does this variable end up being passed to
gcc?

I am tempted to just disable -Werror completely, but at the very least
it should be disabled for BUILT_SOURCES since you can't really fix the
warnings there.  Any advice on how to do this?