Quickstart `make -f` error: `path/to/Makefile is not a directory`

[leogermond]

Describe the bug

When using the quickstart project, calling the Makefile with the --file option (https://www.gnu.org/software/make/manual/make.html#index-_002d_002dfile) results in a weird error:

make -f /path/to/doc/Makefile -j 1 html

Application error:
Output directory (/path/to/doc/Makefile) is not a directory

How to Reproduce

$ mkdir test_sphinx_makefile
$ cd test_sphinx_makefile
$ pip install sphinx
$ sphinx-quickstart
> separate source: n
> project name: test
> project author: test
> project release:
> project language: en
$ cd ..
$ make -f test_sphinx_makefile/Makefile html

Running Sphinx v5.1.0

Configuration error:
config directory doesn't contain a conf.py file (/home/germond/Labs/repro)
make: *** [test_sphinx_makefile/Makefile:20: test_sphinx_makefile/Makefile] Error 2

Error text can vary, the main issue is that the Makefile path is taken as if it were the target.

Expected behavior

A html build should be run and finish successfully, as it would by calling make -C test_sphinx_makefile html

make: Entering directory '/home/germond/Labs/repro/test_sphinx_makefile'
Running Sphinx v5.1.0
making output directory... done
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 1 source files that are out of date
updating environment: [new config] 1 added, 0 changed, 0 removed
reading sources... [100%] index                                                            
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [100%] index                                                             
generating indices... genindex done
writing additional pages... search done
copying static files... done
copying extra files... done
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded.

The HTML pages are in _build/html.

Your project

github.com/adacore/cuda

Screenshots

No response

OS

Linux

Python version

3.8.10

Sphinx version

5.1.0

Sphinx extensions

No response

Extra tools

No response

Additional context

No response

[jfbu]

I think problems are to be expected from make -f if the make is not executed from same directory as where Makefile resides, correct way is make -C then. (cf discussion at #10707). At my locale make -f Makefile html works already, if executed from soure directory (make -f /path/to/Makefile html from another location does not work).

Can you check if https://github.com/jfbu/sphinx/commit/a9c2c7f24608ec1d3ae689638d67cd9740e1c80f works, in the sense of allowing make -f RenamedMakefile html (from source directory).