[libpng16] Fixed CMakelists.txt to allow building a single variant of the
library (Claudio Bley):
Introduced a PNG_LIB_TARGETS variable that lists all activated library
targets. It is an error if this variable ends up empty, ie. you have
to build at least one library variant.
Made the *_COPY targets only depend on library targets actually being build.
Use PNG_LIB_TARGETS to unify a code path.
Changed the CREATE_SYMLINK macro to expact the full path to a file as the
first argument. When symlinking the filename component of that path is
determined and used as the link target.
Use copy_if_different in the CREATE_SYMLINK macro.
3 files changed
