bug#57959: 29.0.50; build error on gnulinux

[Gregory Heytings]

> > What's the exact "make" command you type?  Can you try "git clean -fdx" 
> > followed by "make" (without any other arguments, except -j<some 
> > number>)?
>
> Yes. If I run just "make -j`nproc`" after "git clean -fdx", it builds 
> fine. Following is my observation now,
>
> # bad
> git clean -fdx
> make -j`nproc` configure="--prefix=$HOME/.local" install
>
> # bad
> ./autogen.sh
> ./configure --prefix=$HOME/.local
> make -j`nproc` install
>
> # good
> ./autogen.sh
> ./configure --prefix=$HOME/.local
> make -j`nproc`
> make install
>
> It appears that the "install" target has some issues with "-j`nproc`" if 
> the emacs is not already built.

This should now be fixed on master.  Can you please check, and tell us if 
it's indeed fixed?

(Note that "make install" works, but is not recommended.  It is better to 
do "make && make install", to actually proceed with the install only if 
the build succeeded.)