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/cmQTWrapUICommand.cxx b/Source/cmQTWrapUICommand.cxx
index 2223e2d..361d7b3 100644
--- a/Source/cmQTWrapUICommand.cxx
+++ b/Source/cmQTWrapUICommand.cxx
@@ -132,7 +132,7 @@ bool cmQTWrapUICommand::InitialPass(std::vector<std::string> const& args,
   }
 
   // Store the final list of source files and headers.
-  this->Makefile->AddDefinition(sourceList, sourceListValue.c_str());
-  this->Makefile->AddDefinition(headerList, headerListValue.c_str());
+  this->Makefile->AddDefinition(sourceList, sourceListValue);
+  this->Makefile->AddDefinition(headerList, headerListValue);
   return true;
 }