cmMakefile: Let AddDefinition accept a value as cm::string_view

This changes `cmMakefile::AddDefinition` to take a `cm::string_view` as value
argument instead of a `const char *`.

Benefits are:
- `std::string` can be passed to `cmMakefile::AddDefinition` directly without
  the `c_str()` plus string length recomputation fallback.
- Lengths of literals passed to `cmMakefile::AddDefinition` can be computed at
  compile time.

In various sources uses of `cmMakefile::AddDefinition` are adapted to avoid
`std::string::c_str` calls and the `std::string` is passed directly.
Uses of `cmMakefile::AddDefinition`, where a `nullptr` `const char*` might
be passed to `cmMakefile::AddDefinition` are extended with `nullptr` checks.

1 files changed, 1 insertions, 2 deletions

diff --git a/Source/CTest/cmCTestHandlerCommand.cxx b/Source/CTest/cmCTestHandlerCommand.cxx
index 2b73d40..00188e4 100644
--- a/Source/CTest/cmCTestHandlerCommand.cxx
+++ b/Source/CTest/cmCTestHandlerCommand.cxx
@@ -230,8 +230,7 @@ bool cmCTestHandlerCommand::InitialPass(std::vector<std::string> const& args,
   if (this->Values[ct_RETURN_VALUE] && *this->Values[ct_RETURN_VALUE]) {
     std::ostringstream str;
     str << res;
-    this->Makefile->AddDefinition(this->Values[ct_RETURN_VALUE],
-                                  str.str().c_str());
+    this->Makefile->AddDefinition(this->Values[ct_RETURN_VALUE], str.str());
   }
   this->ProcessAdditionalValues(handler);
   // log the error message if there was an error