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, 2 deletions

diff --git a/Source/cmGetPropertyCommand.cxx b/Source/cmGetPropertyCommand.cxx
index 039f439..de462ed 100644
--- a/Source/cmGetPropertyCommand.cxx
+++ b/Source/cmGetPropertyCommand.cxx
@@ -121,7 +121,7 @@ bool cmGetPropertyCommand::InitialPass(std::vector<std::string> const& args,
     } else {
       output = "NOTFOUND";
     }
-    this->Makefile->AddDefinition(this->Variable, output.c_str());
+    this->Makefile->AddDefinition(this->Variable, output);
   } else if (this->InfoType == OutFullDoc) {
     // Lookup full documentation.
     std::string output;
@@ -132,7 +132,7 @@ bool cmGetPropertyCommand::InitialPass(std::vector<std::string> const& args,
     } else {
       output = "NOTFOUND";
     }
-    this->Makefile->AddDefinition(this->Variable, output.c_str());
+    this->Makefile->AddDefinition(this->Variable, output);
   } else if (this->InfoType == OutDefined) {
     // Lookup if the property is defined
     if (this->Makefile->GetState()->GetPropertyDefinition(this->PropertyName,