Implicit link information contains architecture-specific libraries and
directories. The link information cannot be explicitly specified safely
when CMAKE_OSX_ARCHITECTURES contains more than one architecture.
As a result, we currently cannot support mixed-language C++/Fortran
targets and OS X universal binaries simultaneously. In order to avoid
conflicts for simple C/C++ cases, we now simply skip detection of
implicit link information in this case.
Xcode adds extra link directories that point at the build tree, so
detection of implicit link directories is not reliable. Since Fortran
is not supported in Xcode we will not need implicit link information yet
anyway.
This teaches CMake to detect implicit link information for C, C++, and
Fortran compilers. We detect the implicit linker search directories and
implicit linker options for UNIX-like environments using verbose output
from compiler front-ends. We store results in new variables called
CMAKE_<LANG>_IMPLICIT_LINK_LIBRARIES
CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES
The implicit libraries can contain linker flags as well as library
names.
Bill Hoffman
Brad King