devel/glib20: fix symlink writing

$ gio save testfile < /etc/shells
$ ln -s testfile testlink
$ gio save testlink < /etc/shells
gio: file:///path/to/testlink: Error opening file '/path/to/testlink': Too many links

PR: 212572
Reported by: Yuri Victorovich
Submitted by: Ting-Wei Lan
Approved by: maintainer timeout (3 weeks)
MFH: 2017Q2