run_cmd: Default to environment from global context

If env is not provided, use the global context environment. Then drop
all every passing of that parameter.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/build.py

@@ -122,4 +122,4 @@ class BuildCommand(Command):
         bitbake = find_program(ctx.environ['PATH'], 'bitbake')
         run_cmd(([bitbake, '-k', '-c', ctx.config.get_bitbake_task()]
                  + ctx.config.get_bitbake_targets()),
-                env=ctx.environ, cwd=ctx.build_dir)
+                cwd=ctx.build_dir)