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, 1 insertions, 2 deletions

diff --git a/Source/cmGlobalVisualStudio8Generator.cxx b/Source/cmGlobalVisualStudio8Generator.cxx
index 85ddc85..cc6e421 100644
--- a/Source/cmGlobalVisualStudio8Generator.cxx
+++ b/Source/cmGlobalVisualStudio8Generator.cxx
@@ -54,8 +54,7 @@ void cmGlobalVisualStudio8Generator::EnableLanguage(
 void cmGlobalVisualStudio8Generator::AddPlatformDefinitions(cmMakefile* mf)
 {
   if (this->TargetsWindowsCE()) {
-    mf->AddDefinition("CMAKE_VS_WINCE_VERSION",
-                      this->WindowsCEVersion.c_str());
+    mf->AddDefinition("CMAKE_VS_WINCE_VERSION", this->WindowsCEVersion);
   }
 }