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/cmGlobalVisualStudio10Generator.cxx b/Source/cmGlobalVisualStudio10Generator.cxx
index 55374a4..4a3cadd 100644
--- a/Source/cmGlobalVisualStudio10Generator.cxx
+++ b/Source/cmGlobalVisualStudio10Generator.cxx
@@ -445,7 +445,7 @@ bool cmGlobalVisualStudio10Generator::InitializeSystem(cmMakefile* mf)
     this->DefaultPlatformName = "Tegra-Android";
     this->DefaultPlatformToolset = "Default";
     this->NsightTegraVersion = v;
-    mf->AddDefinition("CMAKE_VS_NsightTegra_VERSION", v.c_str());
+    mf->AddDefinition("CMAKE_VS_NsightTegra_VERSION", v);
   }
 
   return true;
@@ -659,8 +659,7 @@ bool cmGlobalVisualStudio10Generator::FindMakeProgram(cmMakefile* mf)
   if (!this->cmGlobalVisualStudio8Generator::FindMakeProgram(mf)) {
     return false;
   }
-  mf->AddDefinition("CMAKE_VS_MSBUILD_COMMAND",
-                    this->GetMSBuildCommand().c_str());
+  mf->AddDefinition("CMAKE_VS_MSBUILD_COMMAND", this->GetMSBuildCommand());
   return true;
 }