Disable dot(1) because it can break when run under dpb(1).

e.g.
/usr/local/bin/gi-docgen generate --quiet --fatal-warnings \
        --config doc/libgweather.toml --output-dir=doc/libgweather-4.0 \
        --no-namespace-dir \
        --content-dir=/hack/objdirs/pobj/libgweather4-4.0.0/libgweather-4.0.0/doc \
        libgweather/GWeather-4.0.gir
WARNING: Unable to process dot data: b'Fontconfig error:
No writable cache directories\nFontconfig error: No writable cache directories\n'

This happens if there's an empty directory under one of the fontconfig paths
(most likely /usr/local/share/fonts/) which probably happens during dpb(1)
junking (which is why it doesn't happen in every bulks).

issue reported by several over the past months (most notably naddy@ and tb@)

textproc/gi-docgen/Makefile

@@ -2,6 +2,7 @@ COMMENT=		documentation generator for GObject-based libraries
 
 GNOME_PROJECT=		gi-docgen
 GNOME_VERSION=		2022.1
+REVISION=		0
 
 # override gnome MODULE
 MASTER_SITES ?=         ${MASTER_SITE_GNOME:=sources/${GNOME_PROJECT}/${GNOME_VERSION:C/^([0-9]+)\..*/\1/}/}

textproc/gi-docgen/patches/patch-gidocgen_config_py

@@ -0,0 +1,29 @@
+XXX disable dot(1) because it can break when run under dpb(1).
+
+e.g.
+/usr/local/bin/gi-docgen generate --quiet --fatal-warnings \
+	--config doc/libgweather.toml --output-dir=doc/libgweather-4.0 \
+	--no-namespace-dir \
+	--content-dir=/hack/objdirs/pobj/libgweather4-4.0.0/libgweather-4.0.0/doc \
+	libgweather/GWeather-4.0.gir
+WARNING: Unable to process dot data: b'Fontconfig error:
+No writable cache directories\nFontconfig error: No writable cache directories\n'
+
+This happens if there's an empty directory under one of the fontconfig paths
+(most likely /usr/local/share/fonts/) which probably happens during dpb(1)
+junking (which is why it doesn't happen in every bulks).
+
+Index: gidocgen/config.py
+--- gidocgen/config.py.orig
++++ gidocgen/config.py
+@@ -161,9 +161,7 @@ class GIDocConfig:
+ 
+     @property
+     def show_class_hierarchy(self):
+-        if utils.find_program('dot') is None:
+-            return False
+-        return self.theme.get('show_class_hierarchy', False)
++        return False
+ 
+     def source_link(self, *args):
+         (filename, line) = args[0]