BLD: Strip extra newline when dumping gfortran version on MacOS

[kchoudhu]

No description provided.

[charris]

For documentation, what problems does the extra newline cause?

[charris]

Thanks @kchoudhu .

[kchoudhu]

Thanks for the merge -- pkgsrc users thank you!

For documentation, what problems does the extra newline cause?

Under certain circumstances on MacOS, gfortran will output two newlines instead of just the one, like so:

"warning: couldn't understand version 11.2\n\n7.5.0"

When this happens, the detected version string is "\n7.5.0", and falls through the version classification code.

strip()-ing the whitespace fixes the problem.