gnucash unstable: [MacOS]Conditionally set -Wno-unused-local-typedef and -Wno-unknown-attributes.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/e6edb9d8 (commit)
	from  https://github.com/Gnucash/gnucash/commit/eb1400c4 (commit)



commit e6edb9d8e75a3817dd5556e631c3900ad87e8d68
Author: John Ralls <jralls at ceridwen.us>
Date:   Sat Feb 3 07:54:37 2018 -0800

    [MacOS]Conditionally set -Wno-unused-local-typedef and -Wno-unknown-attributes.
    
    These flags aren't defined until Xcode8.



Summary of changes:
 CMakeLists.txt | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)