FTB docs

[JiffB]

Ze bug

Hi,
I followed the git mod'op and 25.3.2.10 built like charm, however :

KERL_BUILD_DOCS=yes kerl build 25.3-builtdocs
failed with : 
ERROR: '25.3_builtdocs' is not a valid Erlang/OTP release

I also tried replacing 25.3 with 25.3.2.10 but got the same answer.

NB: At this stage, I did not already installed this kerl compilation (that will go into /usr/local/erlang/25.3 when the docs problem will be solved).

Software versions

A list of software versions where the bug is apparent, as detailed as possible:

• Operating System: Debian bullseye on a NanoPC-T6 (aarch64 - CPU: RK3588)
• Erlang/OTP: None installed
• kerl: Git master version

How to replicate

An ordered list of steps to replicate the bug, e.g.:

1. run kerl build 25.3
2. run KERL_BUILD_DOCS=yes kerl build 25.3-builtdocs
3. got ERROR: '25.3-builtdocs' is not a valid Erlang/OTP release.

Expected behaviour

Erlang docs to build as easily as Erlang executables

Additional context

An old tarball compilation (25.3.2.5) was manually removed as there's no uninstall in its Makefile (man pages not removed, no time for that) before using kerl.