Checklist

• I have followed every step on the compiling wiki page and
  installed all necessary dependencies.
• My problem is not described on the known issues page
• I have searched for other open and closed issues that
  may have already reported this problem.
• I was able to reproduce this build issue in a clean build

Build Process

How did you build polybar?

• By cloning this repository (What is the output of git describe --tags?)
• 3.5.5 (also tested olders versions)

./build.sh

Build Log

CMake Error at doc/cmake_install.cmake:50 (file):
  file INSTALL cannot find
  "/home/florian/programs/polybar/build/doc/man/polybar.1": No such file or
  directory.
Call Stack (most recent call first):
  cmake_install.cmake:51 (include)


make: *** [Makefile:83: install] Error 1
** Failed to install executables...

Additional context

Due to the new Sphinx 4.0.0 release /home/florian/programs/polybar/build/doc/man/polybar.1 doesn't exist, instead /home/florian/programs/polybar/build/doc/man/1/polybar.1 is generated. And therefore INSTALL cannot find it.

Downgrading Sphinx to 3.5.4 solved the issue.