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/cmTryRunCommand.cxx b/Source/cmTryRunCommand.cxx
index a92c2a0..ed944ac 100644
--- a/Source/cmTryRunCommand.cxx
+++ b/Source/cmTryRunCommand.cxx
@@ -137,7 +137,7 @@ bool cmTryRunCommand::InitialPass(std::vector<std::string> const& argv,
       // now put the output into the variables
       if (!this->RunOutputVariable.empty()) {
         this->Makefile->AddDefinition(this->RunOutputVariable,
-                                      runOutputContents.c_str());
+                                      runOutputContents);
       }
 
       if (!this->OutputVariable.empty()) {
@@ -148,8 +148,7 @@ bool cmTryRunCommand::InitialPass(std::vector<std::string> const& argv,
         if (compileOutput) {
           runOutputContents = compileOutput + runOutputContents;
         }
-        this->Makefile->AddDefinition(this->OutputVariable,
-                                      runOutputContents.c_str());
+        this->Makefile->AddDefinition(this->OutputVariable, runOutputContents);
       }
     }
   }