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/cmBuildCommand.cxx b/Source/cmBuildCommand.cxx
index 428a0b2..e9e1d49 100644
--- a/Source/cmBuildCommand.cxx
+++ b/Source/cmBuildCommand.cxx
@@ -92,7 +92,7 @@ bool cmBuildCommand::MainSignature(std::vector<std::string> const& args)
     this->Makefile->GetGlobalGenerator()->GenerateCMakeBuildCommand(
       target, configuration, "", this->Makefile->IgnoreErrorsCMP0061());
 
-  this->Makefile->AddDefinition(variable, makecommand.c_str());
+  this->Makefile->AddDefinition(variable, makecommand);
 
   return true;
 }