Add missing but expected as exception clause
The `except` line was missing its `as e` clause.
As a result, when erroring out, after not finding a compiler, Meson
gives an error ending:
```
File "C:\Users\Matthew\AppData\Roaming\Python\Python39\site-packages\mesonbuild\mesonlib\vsenv.py",
line 100, in setup_vsenv
mlog.warning('Failed to activate VS environment:', str(e))
```
@@ -94,7 +94,7 @@ def _setup_vsenv(force: bool) -> bool:
def setup_vsenv(force: bool = False):
try:
_setup_vsenv(force)
- except MesonException:
+ except MesonException as e:
if force:
raise
mlog.warning('Failed to activate VS environment:', str(e))
