Restrict '-std=gnu99' wcslib build flag to 'unix'
Restrict '-std=gnu99' wcslib build flag to 'unix'

mhvk/astropy,aleksandr-bakanov/astropy,pllim/astropy,pllim/astropy,astropy/astropy,StuartLittlefair/astropy,lpsinger/astropy,pllim/astropy,saimn/astropy,StuartLittlefair/astropy,astropy/astropy,pllim/astropy,lpsinger/astropy,lpsinger/astropy,lpsinger/astropy,larrybradley/astropy,larrybradley/astropy,mhvk/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,saimn/astropy,larrybradley/astropy,mhvk/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,astropy/astropy,lpsinger/astropy,pllim/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,astropy/astropy,mhvk/astropy,saimn/astropy,astropy/astropy,saimn/astropy,larrybradley/astropy