Source sweep: Use cmStrCat for string concatenation

This patch is generated by a python script that uses regular expressions to
search for string concatenation patterns of the kind

```
std::string str = <ARG0>;
str += <ARG1>;
str += <ARG2>;
...
```

and replaces them with a single `cmStrCat` call

```
std::string str = cmStrCat(<ARG0>, <ARG1>, <ARG2>, ...);
```

If any `<ARGX>` is itself a concatenated string of the kind

```
a + b + c + ...;
```

then `<ARGX>` is split into multiple arguments for the `cmStrCat` call.

If there's a sequence of literals in the `<ARGX>`, then all literals in the
sequence are concatenated and merged into a single literal argument for
the `cmStrCat` call.

Single character strings are converted to single char arguments for
the `cmStrCat` call.

`std::to_string(...)` wrappings are removed from `cmStrCat` arguments,
because it supports numeric types as well as string types.

`arg.substr(x)` arguments to `cmStrCat` are replaced with
`cm::string_view(arg).substr(x)`

1 files changed, 2 insertions, 4 deletions

diff --git a/Source/cmOutputRequiredFilesCommand.cxx b/Source/cmOutputRequiredFilesCommand.cxx
index de47ce0..38e86e3 100644
--- a/Source/cmOutputRequiredFilesCommand.cxx
+++ b/Source/cmOutputRequiredFilesCommand.cxx
@@ -193,10 +193,8 @@ protected:
         // see if the include matches the regular expression
         if (!this->IncludeFileRegularExpression.find(includeFile)) {
           if (this->Verbose) {
-            std::string message = "Skipping ";
-            message += includeFile;
-            message += " for file ";
-            message += info->FullPath;
+            std::string message =
+              cmStrCat("Skipping ", includeFile, " for file ", info->FullPath);
             cmSystemTools::Error(message);
           }
           continue;