file: Fix formatting of error in SIZE sub-command

Source/cmFileCommand.cxx

@@ -3630,7 +3630,7 @@ bool cmFileCommand::HandleSizeCommand(std::vector<std::string> const& args)
 
   if (!cmSystemTools::FileExists(filename, true)) {
     std::ostringstream e;
-    e << "SIZE requested of path that is not readable " << filename;
+    e << "SIZE requested of path that is not readable:\n  " << filename;
     this->SetError(e.str());
     return false;
   }

Tests/RunCMake/file/SIZE-error-does-not-exist-stderr.txt

@@ -1,5 +1,6 @@
 ^CMake Error at SIZE-error-does-not-exist.cmake:[0-9]+ \(file\):
-  file SIZE requested of path that is not readable
-  /a/file/that/does-not-exist
+  file SIZE requested of path that is not readable:
+
+    .*/Tests/RunCMake/file/SIZE-error-does-not-exist-build/does-not-exist
 Call Stack \(most recent call first\):
   CMakeLists.txt:[0-9]+ \(include\)

Tests/RunCMake/file/SIZE-error-does-not-exist.cmake

@@ -1,3 +1,3 @@
-set(file "/a/file/that/does-not-exist")
+set(file "${CMAKE_CURRENT_BINARY_DIR}/does-not-exist")
 
 file(SIZE "${file}" CALCULATED_SIZE)