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/cmGlobalVisualStudio7Generator.cxx b/Source/cmGlobalVisualStudio7Generator.cxx
index 8764ee4..8401efb 100644
--- a/Source/cmGlobalVisualStudio7Generator.cxx
+++ b/Source/cmGlobalVisualStudio7Generator.cxx
@@ -121,8 +121,7 @@ bool cmGlobalVisualStudio7Generator::FindMakeProgram(cmMakefile* mf)
   if (!this->cmGlobalVisualStudioGenerator::FindMakeProgram(mf)) {
     return false;
   }
-  mf->AddDefinition("CMAKE_VS_DEVENV_COMMAND",
-                    this->GetDevEnvCommand().c_str());
+  mf->AddDefinition("CMAKE_VS_DEVENV_COMMAND", this->GetDevEnvCommand());
   return true;
 }
 
@@ -268,7 +267,7 @@ bool cmGlobalVisualStudio7Generator::SetSystemName(std::string const& s,
                                                    cmMakefile* mf)
 {
   mf->AddDefinition("CMAKE_VS_INTEL_Fortran_PROJECT_VERSION",
-                    this->GetIntelProjectVersion().c_str());
+                    this->GetIntelProjectVersion());
   return this->cmGlobalVisualStudioGenerator::SetSystemName(s, mf);
 }