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, 1 deletions

diff --git a/Source/cmSetCommand.cxx b/Source/cmSetCommand.cxx
index 41555e8..b36878c 100644
--- a/Source/cmSetCommand.cxx
+++ b/Source/cmSetCommand.cxx
@@ -154,7 +154,7 @@ bool cmSetCommand::InitialPass(std::vector<std::string> const& args,
                                        type, force);
   } else {
     // add the definition
-    this->Makefile->AddDefinition(variable, value.c_str());
+    this->Makefile->AddDefinition(variable, value);
   }
   return true;
 }