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, 4 insertions, 2 deletions

diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index e685644..18b81d4 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -17,6 +17,8 @@
 #include <unordered_map>
 #include <vector>
 
+#include "cm_string_view.hxx"
+
 #include "cmAlgorithms.h"
 #include "cmFunctionBlocker.h"
 #include "cmListFileCache.h"
@@ -263,11 +265,11 @@ public:
    * Add a variable definition to the build. This variable
    * can be used in CMake to refer to lists, directories, etc.
    */
-  void AddDefinition(const std::string& name, const char* value);
+  void AddDefinition(const std::string& name, cm::string_view value);
   /**
    * Add bool variable definition to the build.
    */
-  void AddDefinitionBool(const std::string& name, bool value);
+  void AddDefinitionBool(const std::string& name, bool);
   //! Add a definition to this makefile and the global cmake cache.
   void AddCacheDefinition(const std::string& name, const char* value,
                           const char* doc, cmStateEnums::CacheEntryType type,