Don't include generator expressions in old-style link handling.

Don't add generator expressions to variables which are used
for CMP0003, CMP0004, and the old-style _LIB_DEPENDS content. They
will not be evaluated when read anyway and would probably confuse
the code reading them.

This makes it legitimate to use target_link_libraries with generator
expressions as arguments.

Source/cmTarget.cxx

@@ -2232,6 +2232,14 @@ static std::string targetNameGenex(const char *lib)
   return std::string("$<TARGET_NAME:") + lib + ">";
 }
 
+//----------------------------------------------------------------------------
+static bool isGeneratorExpression(const std::string &lib)
+{
+  const std::string::size_type openpos = lib.find("$<");
+  return (openpos != std::string::npos)
+      && (lib.find(">", openpos) != std::string::npos);
+}
+
 //----------------------------------------------------------------------------
 void cmTarget::AddLinkLibrary(cmMakefile& mf,
                               const char *target, const char* lib,
@@ -2254,6 +2262,11 @@ void cmTarget::AddLinkLibrary(cmMakefile& mf,
                                                           llt).c_str());
   }
 
+  if (isGeneratorExpression(lib))
+    {
+    return;
+    }
+
   cmTarget::LibraryID tmp;
   tmp.first = lib;
   tmp.second = llt;

Source/cmTargetLinkLibrariesCommand.h

@@ -13,6 +13,7 @@
 #define cmTargetLinkLibrariesCommand_h
 
 #include "cmCommand.h"
+#include "cmDocumentGeneratorExpressions.h"
 
 /** \class cmTargetLinkLibrariesCommand
  * \brief Specify a list of libraries to link into executables.
@@ -141,6 +142,12 @@ public:
       "However, if two archives are really so interdependent they should "
       "probably be combined into a single archive."
       ")"
+      "\n"
+      "Arguments to target_link_libraries may use \"generator expressions\" "
+      "with the syntax \"$<...>\".  Note however, that generator expressions "
+      "will not be used in OLD handling of CMP0003 or CMP0004."
+      "\n"
+      CM_DOCUMENT_COMMAND_GENERATOR_EXPRESSIONS
       ;
     }