CI: Confluence page: Fix not created mx6 section

The function that merges the variables of the different jobs, i.e:

`MACHINE="mx6"`

`MACHINE="mx6ull"`

used python `in` to check if a value already exists.
But `"mx6" in "mx6ull"` is true, so mx6 was dropped.
This rewrites it, storing the variables in a set (which is unique
automatically) instead of space seperated strings.
Space seperation is added before printing the variables to be used on
on the shell.

scripts/collect_release_information.py

@@ -30,7 +30,7 @@ def get_job_env_variables(
         env_file: name of the GitLab dotenv file to read variables from
 
     Returns:
-        Dictionary of variables with 'name' and 'value' fields
+        Dictionary of variables with 'name' and an set of 'value' fields
     """
     variables = {}
 
@@ -52,7 +52,11 @@ def get_job_env_variables(
         for line in lines:
             name, value = line.partition("=")[::2]
             value = value.strip("'\" ")
-            variables[name] = value
+            if name not in variables.keys():
+                variables[name] = set()
+            for elem in value.split(" "):
+                if len(elem) > 0:
+                    variables[name].add(elem)
 
     return variables
 
@@ -94,24 +98,26 @@ def get_pipeline_variable_value(variables: ProjectPipelineVariableManager, key:
     return variable.value
 
 
-def merge_variables(first: dict[str, str], second: dict[str, str]) -> dict[str, str]:
-    """Merge two dictionaries of variables. If a variable exists in both dictionaries
-       and one value is not already contained in the other, concatenate its values with
-       a space in between.
+def merge_variables(
+    first: dict[str, set[str]], second: dict[str, set[str]]
+) -> dict[str, set[str]]:
+    """Merge two dictionaries of variables, each variable stored as set.
+       If a variable exists in both dictionaries the values are merged into one
+       without duplicates.
 
     Args:
         first: a dictionary containing variables
-        secondary: a dictionary containing variables
+        second: a dictionary containing variables
 
     Returns:
         A dictionary containing merged variables
     """
     merged = first
-    for key in second:
-        if key not in first or first[key] in second[key]:
-            merged[key] = second[key]
-        elif second[key] not in first[key]:
-            merged[key] = f"{first[key]} {second[key]}"
+    for key, value in second.items():
+        if key not in first:
+            merged[key] = value
+        else:
+            merged[key] |= value
     return merged
 
 
@@ -169,6 +175,10 @@ def main():
     )
 
     # Get all parallel child pipelines with the same Confluence configuration
+    # For example the yocto build pipeline and the sdk pipeline should end up
+    # and the same confluence page, so both need to be found
+    # To find it, go up on level in the pipeline hierarchy and search child pipelines
+    # with the same confluence destination
     pipelines = []
     parent_pipeline = get_parent_pipeline(project, pipeline)
     if parent_pipeline:
@@ -241,7 +251,7 @@ def main():
 
     # Print all variables in a shell compatible form
     for k, v in sorted(variables.items()):
-        print(f'{k}="{v}"')
+        print(f'{k}="{" ".join(v)}"')
 
 
 if __name__ == "__main__":