[cmake] honor $VCPKG_ROOT from env (#83003)

Author: tessro

CMakePresets.json

@@ -24,9 +24,6 @@
       "displayName": "Windows x64 MSVC",
       "description": "Target Windows (64-bit) with the Visual Studio development environment.",
       "generator": "Visual Studio 17 2022",
-      "environment": {
-        "VCPKG_ROOT": "C:/vcpkg"
-      },
       "cacheVariables": {
         "DYNAMIC_LINKING": "False",
         "CURSES": "True", "LOCALIZE": "True", "TILES": "False", "SOUND": "False", "TESTS": "True",
@@ -55,9 +52,6 @@
       "description": "Target Windows (64-bit) with the Visual Studio development environment.",
       "generator": "Visual Studio 17 2022",
       "inherits": "windows-tiles-sounds-x64",
-      "environment": {
-        "VCPKG_ROOT": "C:/vcpkg"
-      },
       "cacheVariables": {
         "CMAKE_PROJECT_INCLUDE_BEFORE": "${sourceDir}/build-scripts/${presetName}.cmake",
         "CMAKE_TOOLCHAIN_FILE": "${sourceDir}/build-scripts/MSVC.cmake",

build-scripts/MSVC.cmake

@@ -85,9 +85,17 @@ set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 # Where is vcpkg.json ?
 set(VCPKG_MANIFEST_DIR ${CMAKE_SOURCE_DIR}/msvc-full-features)
 
-set(VCPKG_ROOT "" CACHE PATH "Path to VCPKG installation")
-if (NOT $ENV{VCPKG_ROOT} STREQUAL "")
-    include($ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)
-elseif(NOT $CACHE{VCPKG_ROOT} STREQUAL "")
-    include($CACHE{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)
+set(VCPKG_ROOT "$ENV{VCPKG_ROOT}" CACHE PATH "Path to VCPKG installation")
+if(NOT VCPKG_ROOT)
+    set(VCPKG_ROOT "C:/vcpkg" CACHE PATH "Path to VCPKG installation" FORCE)
 endif()
+
+set(_vcpkg_toolchain "${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake")
+if(NOT EXISTS "${_vcpkg_toolchain}")
+  message(FATAL_ERROR
+    "Could not find vcpkg toolchain file at:\n  ${_vcpkg_toolchain}\n"
+    "Check that VCPKG_ROOT points to a valid vcpkg checkout "
+    "(it should contain scripts/buildsystems/vcpkg.cmake).")
+endif()
+
+include("${_vcpkg_toolchain}")