Repository: yt-dlp
Issue: Incorrect MARKDOWN initialization in Makefile
Labels: bug,docs/meta/cleanup,PR-needed

### Checklist

- [X] I'm reporting a bug unrelated to a specific site
- [X] I've verified that I'm running yt-dlp version **2022.04.08** ([update instructions](https://github.com/yt-dlp/yt-dlp#update)) or later (specify commit)
- [X] I've checked that all provided URLs are alive and playable in a browser
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/ytdl-org/youtube-dl#video-url-contains-an-ampersand-and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues including closed ones. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)

### Description

On my system pandoc is a symbolic link to /usr/bin/true and this fact leads to following line appearing in stderr when invoking make:
/bin/sh: line 1: [: =: unary operator expected

Following path "fixes" that
```diff
diff --git a/Makefile b/Makefile
index 179aaff57..7fa4a6d46 100644
--- a/Makefile
+++ b/Makefile
@@ -42,7 +42,7 @@ PYTHON ?= /usr/bin/env python3
 SYSCONFDIR = $(shell if [ $(PREFIX) = /usr -o $(PREFIX) = /usr/local ]; then echo /etc; else echo $(PREFIX)/etc; fi)
 
 # set markdown input format to "markdown-smart" for pandoc version 2 and to "markdown" for pandoc prior to version 2
-MARKDOWN = $(shell if [ `pandoc -v | head -n1 | cut -d" " -f2 | head -c1` = "2" ]; then echo markdown-smart; else echo markdown; fi)
+MARKDOWN = $(shell if [ "$(pandoc -v | head -n1 | cut -d" " -f2 | head -c1)" = "2" ]; then echo markdown-smart; else echo markdown; fi)
 
 install: lazy-extractors yt-dlp yt-dlp.1 completions
 	mkdir -p $(DESTDIR)$(BINDIR)
```

### Verbose log

```shell
- make
/usr/bin/env python3 devscripts/make_contributing.py README.md CONTRIBUTING.md
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/1_broken_site.yml .github/ISSUE_TEMPLATE/1_broken_site.yml
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/2_site_support_request.yml .github/ISSUE_TEMPLATE/2_site_support_request.yml
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/3_site_feature_request.yml .github/ISSUE_TEMPLATE/3_site_feature_request.yml
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/4_bug_report.yml .github/ISSUE_TEMPLATE/4_bug_report.yml
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/5_feature_request.yml .github/ISSUE_TEMPLATE/5_feature_request.yml
/usr/bin/env python3 devscripts/make_issue_template.py .github/ISSUE_TEMPLATE_tmpl/6_question.yml .github/ISSUE_TEMPLATE/6_question.yml
/usr/bin/env python3 devscripts/make_supportedsites.py supportedsites.md
/bin/sh: line 1: [: =: unary operator expected
pandoc -f markdown -t plain README.md -o README.txt
/bin/sh: line 1: [: =: unary operator expected
/usr/bin/env python3 devscripts/prepare_manpage.py yt-dlp.1.temp.md
pandoc -s -f markdown -t man yt-dlp.1.temp.md -o yt-dlp.1
rm -f yt-dlp.1.temp.md
```