Restore handling of build directory inside a symlinked path

In commit dd8365b3f1 (Merge branch 'upstream-KWSys' into update-kwsys,
2020-04-06, v3.18.0-rc1~397^2) we imported KWSys commit `019afb6ea`
(SystemTools: Drop GetCurrentWorkingDirectory 'collapse' argument,
2020-04-03).  That caused `GetCurrentWorkingDirectory` to no longer send
paths through the KWSys translation map and broke CMake's detection of
the absolute path to a build directory containing a symbolic link.
Add our own `cmSystemTools::GetCurrentWorkingDirectory` wrapper around
the KWSys method in order to restore that mapping.

Test-case-by: Ben Boeckel <ben.boeckel@kitware.com>
Issue: #16228
Fixes: #20900

Source/CPack/cpack.cxx

@@ -312,7 +312,7 @@ int main(int argc, char const* const* argv)
     // The value has not been set on the command line
     else {
       // get a default value (current working directory)
-      cpackProjectDirectory = cmsys::SystemTools::GetCurrentWorkingDirectory();
+      cpackProjectDirectory = cmSystemTools::GetCurrentWorkingDirectory();
       // use default value if no value has been provided by the config file
       if (!globalMF.IsSet("CPACK_PACKAGE_DIRECTORY")) {
         globalMF.AddDefinition("CPACK_PACKAGE_DIRECTORY",

Source/cmSystemTools.cxx

@@ -2080,6 +2080,12 @@ std::string const& cmSystemTools::GetCMakeRoot()
   return cmSystemToolsCMakeRoot;
 }
 
+std::string cmSystemTools::GetCurrentWorkingDirectory()
+{
+  return cmSystemTools::CollapseFullPath(
+    cmsys::SystemTools::GetCurrentWorkingDirectory());
+}
+
 void cmSystemTools::MakefileColorEcho(int color, const char* message,
                                       bool newline, bool enabled)
 {

Source/cmSystemTools.h

@@ -390,6 +390,9 @@ public:
   static std::string const& GetCMClDepsCommand();
   static std::string const& GetCMakeRoot();
 
+  /** Get the CWD mapped through the KWSys translation map.  */
+  static std::string GetCurrentWorkingDirectory();
+
   /** Echo a message in color using KWSys's Terminal cprintf.  */
   static void MakefileColorEcho(int color, const char* message, bool newLine,
                                 bool enabled);