Make CMAKE_LINK_LIBRARY_FILE_FLAG work like CMAKE_LINK_LIBRARY_FLAG

The `CMAKE_LINK_LIBRARY_FILE_FLAG` variable is meant for linkers that
want library file paths to be preceded by a flag.  This is used only
for OpenWatcom to add the `library` argument before library file paths.
Refactor the approach to treat `CMAKE_LINK_LIBRARY_FILE_FLAG` as a
command-line string fragment to add just before the library file path.
This has two advantages:

* `CMAKE_LINK_LIBRARY_FILE_FLAG` now works like `CMAKE_LINK_LIBRARY_FLAG`.
* `CMAKE_LINK_LIBRARY_FILE_FLAG` can now be an attached flag whose value
  is the library file path.

Technically this is a change in behavior, but this setting was created
for internal use and should be rarely used outside of CMake itself.

Fixes: #19541

Modules/Platform/Windows-OpenWatcom.cmake

@@ -10,7 +10,7 @@ set(__WINDOWS_OPENWATCOM 1)
 
 set(CMAKE_LIBRARY_PATH_FLAG "libpath ")
 set(CMAKE_LINK_LIBRARY_FLAG "library ")
-set(CMAKE_LINK_LIBRARY_FILE_FLAG "library")
+set(CMAKE_LINK_LIBRARY_FILE_FLAG "library ")
 
 if(CMAKE_VERBOSE_MAKEFILE)
   set(CMAKE_WCL_QUIET)

Source/cmComputeLinkInformation.cxx

@@ -990,11 +990,6 @@ void cmComputeLinkInformation::AddTargetItem(std::string const& item,
     return;
   }
 
-  // If this platform wants a flag before the full path, add it.
-  if (!this->LibLinkFileFlag.empty()) {
-    this->Items.emplace_back(this->LibLinkFileFlag, false);
-  }
-
   // For compatibility with CMake 2.4 include the item's directory in
   // the linker search path.
   if (this->OldLinkDirMode && !target->IsFrameworkOnApple() &&
@@ -1057,11 +1052,6 @@ void cmComputeLinkInformation::AddFullItem(std::string const& item)
     this->OldLinkDirItems.push_back(item);
   }
 
-  // If this platform wants a flag before the full path, add it.
-  if (!this->LibLinkFileFlag.empty()) {
-    this->Items.emplace_back(this->LibLinkFileFlag, false);
-  }
-
   // Now add the full path to the library.
   this->Items.emplace_back(item, true);
 }

Source/cmComputeLinkInformation.h

@@ -56,6 +56,11 @@ public:
   std::string GetChrpathString() const;
   std::set<cmGeneratorTarget const*> const& GetSharedLibrariesLinked() const;
 
+  std::string const& GetLibLinkFileFlag() const
+  {
+    return this->LibLinkFileFlag;
+  }
+
   std::string const& GetRPathLinkFlag() const { return this->RPathLinkFlag; }
   std::string GetRPathLinkString() const;
 

Source/cmLinkLineComputer.cxx

@@ -63,6 +63,7 @@ std::string cmLinkLineComputer::ComputeLinkLibs(cmComputeLinkInformation& cli)
       continue;
     }
     if (item.IsPath) {
+      linkLibs += cli.GetLibLinkFileFlag();
       linkLibs +=
         this->ConvertToOutputFormat(this->ConvertToLinkReference(item.Value));
     } else {