Faillure when adding file to ALL_64_TARGET_OBS in Makefile.in

Hi,

For a test, I've created a new aarch64 file specific to a runtime, and 
I'm trying to add this file to ALL_64_TARGET_OBS macro in Makefile.in in 
GDB.
This step is ok but when I'm configuring GDB then I have to specifiy: 
configure.... --enable-targets=all --enable-64-bit-bfd in order to have 
my new aarch64 added during the build.
Of course, adding  --enable-targets=all make my GDB executable size 
increasing from 30 Mb to 105 Mb. Did I missed something here or is it 
the only way to have my new aarch64 runtime specific file taken in account ?

Thanks.