cmake: detect and show VCPKG in platform flags

Use `VCPKG_TOOLCHAIN` to detect a vcpkg build environment.

Closes #14451

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a7872d18e4978bc7165bceca0b24249c2c9e2adf..4d2caf21cb88f4f6067ea4f06d7f28bdc6c6787f 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,6 +79,9 @@ endif()
 if(MSVC)
   set(_flags "${_flags} MSVC")
 endif()
+if(VCPKG_TOOLCHAIN)
+  set(_flags "${_flags} VCPKG")
+endif()
 message(STATUS "CMake platform flags:${_flags}")
 set(_flags)