lib.ExecContext|.Distro: Ignore stdout_str newline

Ignore newline at the end of Result.stdout_str if only one line of output is wanted from an executed shell command. The output of both uname and mktemp are used wrongly in that regard.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/Distro.py

@@ -78,7 +78,7 @@ class Distro(abc.ABC):
                     ),
                 )
                 raise
-            uname = result.stdout_str.lower()
+            uname = result.stdout_str.strip().lower()
             ret = f'ID={uname}\nVERSION_CODENAME=unknown'
         return ret
 

src/python/jw/pkg/lib/ExecContext.py

@@ -588,7 +588,7 @@ class ExecContext(Base):
             raise Exception(
                 f'Failed to create temporary file on {self.root}: {result.summary}'
             )
-        return result.stdout_str
+        return result.stdout_str.strip()
 
     async def _stat(self, path: str, follow_symlinks: bool) -> StatResult: