ENH: Allow link line computation for static libs

In some cases it may be useful to compute a "link" line for a static
library even though it will not be put in the generated build system.
This removes the assertion which previously diallowed the case.

Source/cmTarget.cxx

@@ -3696,9 +3696,6 @@ cmTargetLinkInterface* cmTarget::ComputeLinkInterface(const char* config)
 cmComputeLinkInformation*
 cmTarget::GetLinkInformation(const char* config)
 {
-  // Link information does not make sense for static libraries.
-  assert(this->GetType() != cmTarget::STATIC_LIBRARY);
-
   // Lookup any existing information for this configuration.
   std::map<cmStdString, cmComputeLinkInformation*>::iterator
     i = this->LinkInformation.find(config?config:"");