scripts/addToolsVersion: properly handle .in vs. .in.2

While most components have their version in the .in file, some
have it in the .in.2 (eg. elf2flt).

Currently, to handle this case, we indiscriminately munge both files,
but this is wrong: in the elf2flt case, if we add a binutils version,
we do not want it to be added to elf2flt, and conversely.

So, for each tool, we need to explicitly know what file to munge.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # Options specific to crosstool-NG acting as a backend

 config IS_A_BACKEND

     string

     option env="CT_IS_A_BACKEND"

 config BACKEND

     bool

     default y if IS_A_BACKEND = "y" || IS_A_BACKEND = "Y"

 config BACKEND_ARCH

     string

     option env="CT_BACKEND_ARCH"

 config BACKEND_KERNEL

     string

     option env="CT_BACKEND_KERNEL"

 config BACKEND_LIBC

     string

     option env="CT_BACKEND_LIBC"