>> A 'make' in a repository clone builds Emacs with the default 
>> configuration options.  It would be useful if those who want to build 
>> Emacs with other configuration options they already know could do that 
>> without going through the three-step ./autogen.sh; ./configure 
>> <options>; make.  Patch attached, with which it becomes possible to 
>> just say e.g.:
>>
>> make configure=--with-x-toolkit=lucid
>
> That sounds useful -- but if we add this, perhaps the normal Makefile 
> should also work this way?  That would be useful when doing bootstraps 
> with new configure options, which currently take two runs through 
> configure, which is a bore.  I.e.,
>
> make configure=--with-x-toolkit=lucid bootstrap
>

Indeed, that makes sense.

I attach a patch with which it is possible to say, with both the 
GNUmakefile or the Makefile:

make bootstrap configure=--with-x-toolkit=lucid

and, to go back to the default configuration:

make bootstrap configure=default