bash-completion: add completion for gstreamer tools

Allow to autocomplete with elements/properties in the devenv using gst-launch or gst-inspect.

gst-env.py

@@ -231,6 +231,8 @@ def setup_gdb(options):
 
     return python_paths
 
+def is_bash_completion_available (options):
+    return  os.path.exists(os.path.join(options.builddir, 'subprojects/gstreamer/data/bash-completion/helpers/gst'))
 
 def get_subprocess_env(options, gst_version):
     env = os.environ.copy()
@@ -516,13 +518,14 @@ if __name__ == "__main__":
                     shutil.copyfileobj(src, tmprc)
             tmprc.write('\nexport PS1="[gst-%s] $PS1"' % gst_version)
             tmprc.flush()
-            bash_completions_files = []
-            for p in BASH_COMPLETION_PATHS:
-                if os.path.exists(p):
-                    bash_completions_files +=  os.listdir(path=p)
-            bc_rc = BC_RC.format(bash_completions=' '.join(bash_completions_files), bash_completions_paths=' '.join(BASH_COMPLETION_PATHS))
-            tmprc.write(bc_rc)
-            tmprc.flush()
+            if is_bash_completion_available(options):
+                bash_completions_files = []
+                for p in BASH_COMPLETION_PATHS:
+                    if os.path.exists(p):
+                        bash_completions_files +=  os.listdir(path=p)
+                bc_rc = BC_RC.format(bash_completions=' '.join(bash_completions_files), bash_completions_paths=' '.join(BASH_COMPLETION_PATHS))
+                tmprc.write(bc_rc)
+                tmprc.flush()
             args.append("--rcfile")
             args.append(tmprc.name)
         elif args[0].endswith('fish'):