Add options to run `ldd -u -r` as a "link-what-you-use" tool

Create a LINK_WHAT_YOU_USE target property and corresponding
CMAKE_LINK_WHAT_YOU_USE variable to enable this behavior.
Extend link commands by running `ldd -u -r` to detect shared
libraries that are linked but not needed.

1 files changed, 15 insertions, 0 deletions

diff --git a/Help/prop_tgt/LINK_WHAT_YOU_USE.rst b/Help/prop_tgt/LINK_WHAT_YOU_USE.rst
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index 0000000..32d6edb
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+++ b/Help/prop_tgt/LINK_WHAT_YOU_USE.rst
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+LINK_WHAT_YOU_USE
+---------------------------
+
+This is a boolean option that when set to ``TRUE`` will automatically run
+``ldd -r -u`` on the target after it is linked. In addition, the linker flag
+``-Wl,--no-as-needed`` will be passed to the target with the link command so
+that all libraries specified on the command line will be linked into the
+target. This will result in the link producing a list of libraries that
+provide no symbols used by this target but are being linked to it.
+This is only applicable to executable and shared library targets and
+will only work when ld and ldd accept the flags used.
+
+This property is initialized by the value of
+the :variable:`CMAKE_LINK_WHAT_YOU_USE` variable if it is set
+when a target is created.