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, 3 deletions

diff --git a/Source/cmCoreTryCompile.cxx b/Source/cmCoreTryCompile.cxx
index f12ef0b..d780af6 100644
--- a/Source/cmCoreTryCompile.cxx
+++ b/Source/cmCoreTryCompile.cxx
@@ -932,7 +932,7 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv,
                                      cmStateEnums::INTERNAL);
 
   if (!outputVariable.empty()) {
-    this->Makefile->AddDefinition(outputVariable, output.c_str());
+    this->Makefile->AddDefinition(outputVariable, output);
   }
 
   if (this->SrcFileSignature) {
@@ -961,8 +961,7 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv,
     }
 
     if (!copyFileError.empty()) {
-      this->Makefile->AddDefinition(copyFileError,
-                                    copyFileErrorMessage.c_str());
+      this->Makefile->AddDefinition(copyFileError, copyFileErrorMessage);
     }
   }
   return res;