meson: Fix support for empty darwin sysroot

Peter Eisentraut <peter.eisentraut@enterprisedb.com>

From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2023-03-22T07:34:00Z
Lists: pgsql-hackers

Attachments

The -isysroot options should only be added if the sysroot resolved to a 
nonempty string.  This matches the behavior in src/template/darwin (also 
documented in installation.sgml).

Commits

  1. meson: Fix support for empty darwin sysroot