tests : add _CRT_SECURE_NO_WARNINGS for WIN32 (#8231)

This commit adds the compile definition `_CRT_SECURE_NO_WARNINGS`
to the root cmake subproject.

The motivation for this is that currently the following warnings are
displayed when compiling the tests and common cmake subprojects:
```console
test-llama-grammar.cpp
C:\llama.cpp\src\.\llama.cpp(1406,77): warning C4996: 'strerror':
This function or variable may be unsafe. Consider using strerror_s
instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See
online help for details.
[C:\llama.cpp\build\tests\test-llama-grammar.vcxproj]
...
```

This compile definition is currently set for the `src` subproject
and this change moves into the root cmake project so that it is applied
to all cmake subprojects.

CMakeLists.txt

@@ -42,6 +42,10 @@ endif()
 
 option(BUILD_SHARED_LIBS "build shared libraries" ${BUILD_SHARED_LIBS_DEFAULT})
 
+if (WIN32)
+    add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
+endif()
+
 #
 # option list
 #

src/CMakeLists.txt

@@ -1,7 +1,5 @@
 # TODO: should not use this
 if (WIN32)
-    add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
-
     if (BUILD_SHARED_LIBS)
         set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
     endif()