[mod] reduce enviroment variables in shell scripts to what is needed

Not all settings from the 'brand:' section of the YAML files are needed in the
shell scripts.  This patch reduce the variables in ./utils/brand.env to what is
needed.  The following ('brand:' settings) can be removed from this file:

- ISSUE_URL
- DOCS_URL
- PUBLIC_INSTANCES
- WIKI_URL

Tasks running outside of an *installed instance*, need the following settings
from the YAML configuration:

- GIT_URL            <--> brand.git_url
- GIT_BRANCH         <--> brand.git_branch
- SEARX_URL          <--> server.base_url  (aka PUBLIC_URL)
- SEARX_PORT         <--> server.port
- SEARX_BIND_ADDRESS <--> server.bind_address

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

utils/build_env.py

@@ -23,14 +23,19 @@ def _env(*arg, **kwargs):
         val = ''
     return val
 
+# If you add or remove variables here, do not forgett to update:
+# - docs/admin/engines/settings.rst
+# - /docs/dev/makefile.rst (section make buildenv)
+
 name_val = [
-    ('SEARX_URL'              , 'server.base_url'),
+
     ('GIT_URL'                , 'brand.git_url'),
     ('GIT_BRANCH'             , 'brand.git_branch'),
-    ('ISSUE_URL'              , 'brand.issue_url'),
-    ('DOCS_URL'               , 'brand.docs_url'),
-    ('PUBLIC_INSTANCES'       , 'brand.public_instances'),
-    ('WIKI_URL'               , 'brand.wiki_url'),
+
+    ('SEARX_URL'              , 'server.base_url'),
+    ('SEARX_PORT'             , 'server.port'),
+    ('SEARX_BIND_ADDRESS'     , 'server.bind_address'),
+
 ]
 
 brand_env = 'utils' + sep + 'brand.env'