Silence missing gfortran errors in `Make.inc` (#48403)
When we attempt to invoke `gfortran` to determine the local `libgfortran` ABI version that we should attempt to mimic, if `gfortran` is not installed we get a harmless error printed out to `stderr`:
```
/bin/sh: line 1: gfortran: command not found
```
This should silence these errors, as they're not useful to us.
