> emacsgtkfixed.c:36: error: redefinition of typedef 'EmacsFixedPrivate'
> ...
> emacsgtkfixed.c:37: error: redefinition of typedef 'EmacsFixedClass'

Thanks for reporting the problem. It looks like you have a picky C99 compiler 
that rejects duplicate typedefs. I installed into the emacs-25 branch the 
attached patch to fix this porting glitch; please give it a try.

The other diagnostics look like you ran './configure FOO-OPTIONS; make; 
./configure BAR-OPTIONS; make', which does not work in general.  When switching 
'configure' options, in general one must start with a fresh tree.  One way to do 
this is to leave the source tree alone and build in a separate directory, e.g.:

tar xf emacs-25.1.50.tar.gz

mkdir build-foo
cd build-foo
../emacs-25.1.50/configure FOO-OPTIONS
make
cd ..

mkdir build-bar
cd build-bar
../emacs-25.1.50/configure BAR-OPTIONS
make
cd ..


So please try something like the above, after installing the attached patch.