Fix ModuleNotFoundError: No module named 'myst_parser'

This should fix this error which appears on RHEL only:

```
Configuration error:
There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/sphinx/config.py", line 326, in eval_config_file
    execfile_(filename, namespace)
  File "/usr/lib/python3.9/site-packages/sphinx/util/pycompat.py", line 88, in execfile_
    exec(code, _globals)
  File "/builddir/build/BUILD/llvm-project-c1d5cc99c6ba8e897ea145dbb2221a155b5e3e5a/llvm/redhat-linux-build/tools/clang/docs/conf.py", line 42, in <module>
    import myst_parser
ModuleNotFoundError: No module named 'myst_parser'
```

See also https://github.com/fedora-llvm-team/llvm-snapshots/issues/492

0001-Remove-myst_parser-dependency-for-RHEL.patch

@@ -0,0 +1,41 @@
+From d8742e9b361e5fd6fee2298b8ea0aeb4671ec05a Mon Sep 17 00:00:00 2001
+From: Nikita Popov <npopov@redhat.com>
+Date: Wed, 22 May 2024 09:39:26 +0200
+Subject: [PATCH] Remove myst_parser dependency for RHEL
+
+---
+ clang/docs/conf.py | 3 +--
+ llvm/docs/conf.py  | 3 +--
+ 2 files changed, 2 insertions(+), 4 deletions(-)
+
+diff --git a/clang/docs/conf.py b/clang/docs/conf.py
+index 4cee382a718f..d2e2198e05d4 100644
+--- a/clang/docs/conf.py
++++ b/clang/docs/conf.py
+@@ -43,8 +43,7 @@ try:
+ 
+     extensions.append("myst_parser")
+ except ImportError:
+-    if not tags.has("builder-man"):
+-        raise
++    pass
+ 
+ 
+ # The encoding of source files.
+diff --git a/llvm/docs/conf.py b/llvm/docs/conf.py
+index 7f2ed5309606..354a41f11280 100644
+--- a/llvm/docs/conf.py
++++ b/llvm/docs/conf.py
+@@ -36,8 +36,7 @@ try:
+ 
+     extensions.append("myst_parser")
+ except ImportError:
+-    if not tags.has("builder-man"):
+-        raise
++    pass
+ 
+ # Automatic anchors for markdown titles
+ from llvm_slug import make_slug
+-- 
+2.44.0
+

patches.spec.inc

@@ -22,3 +22,7 @@ Patch3002:     0001-Always-build-shared-libs-for-LLD.patch
 # redhat-rpm-config.
 Patch9001: 0001-Restore-fopenmp-implicit-rpath-disabled-by-default.patch
 %endif
+
+#region RHEL patches
+Patch9002:     0001-Remove-myst_parser-dependency-for-RHEL.patch
+#endregion

prep.spec.inc

@@ -10,10 +10,16 @@
 # see http://ftp.rpm.org/max-rpm/s1-rpm-inside-macros.html
 %autosetup -N -T -b 0 -n %{src_tarball_dir}
 
+# Apply all patches with number <= 9000
+# See https://rpm-software-management.github.io/rpm/manual/autosetup.html
 %autopatch -M9000 -p1
 
 %if 0%{?fedora} == 38
-%patch -p1 9001
+%patch -p1 -P9001
+%endif
+
+%if %{defined rhel}
+%patch -p1 -P9002
 %endif
 
 #region LLVM preparation