hb-coretext.cc: clean up macosx test

TARGET_OS_OSX was introduced only in late OS versions
so always returns as "0" on older systems.

if !TARGET_OS_IPHONE can work, as it returns as !0 on older
systems where TARGET_OS_IPHONE is not defined, but is not
specific

if TARGET_OS_MAC && !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE)
is both specific and accurate on all systems.
1 file changed