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, 2 insertions, 3 deletions

diff --git a/Source/CTest/cmCTestBuildCommand.cxx b/Source/CTest/cmCTestBuildCommand.cxx
index 2eacaf1..e71eafe 100644
--- a/Source/CTest/cmCTestBuildCommand.cxx
+++ b/Source/CTest/cmCTestBuildCommand.cxx
@@ -156,15 +156,14 @@ bool cmCTestBuildCommand::InitialPass(std::vector<std::string> const& args,
   if (this->Values[ctb_NUMBER_ERRORS] && *this->Values[ctb_NUMBER_ERRORS]) {
     std::ostringstream str;
     str << this->Handler->GetTotalErrors();
-    this->Makefile->AddDefinition(this->Values[ctb_NUMBER_ERRORS],
-                                  str.str().c_str());
+    this->Makefile->AddDefinition(this->Values[ctb_NUMBER_ERRORS], str.str());
   }
   if (this->Values[ctb_NUMBER_WARNINGS] &&
       *this->Values[ctb_NUMBER_WARNINGS]) {
     std::ostringstream str;
     str << this->Handler->GetTotalWarnings();
     this->Makefile->AddDefinition(this->Values[ctb_NUMBER_WARNINGS],
-                                  str.str().c_str());
+                                  str.str());
   }
   return ret;
 }