Reduce required Windows CMake version to 3.14 (#89390)

When we landed the CMake minimum requirement constraint for Visual
Studio 2019, we landed it with minimum version 3.15, since that's what
was shipping with the current version of VS 2019 at the time. Looking at
the release notes of earlier versions, it's clear that earlier versions
of Visual Studio 2019 shipped with version 3.14. See:
https://devblogs.microsoft.com/cppblog/visual-studio-cmake-support-clang-llvm-cmake-3-14-vcpkg-and-performance-improvements/

Looking at release notes for CMake 3.15, there are no features/fixes
introduced in that version that we are dependent on.
https://cmake.org/cmake/help/latest/release/3.15.html

Issue: https://github.com/flutter/flutter/issues/88589
diff --git a/dev/integration_tests/flutter_gallery/windows/CMakeLists.txt b/dev/integration_tests/flutter_gallery/windows/CMakeLists.txt
index 225f9a4..899fe2f 100644
--- a/dev/integration_tests/flutter_gallery/windows/CMakeLists.txt
+++ b/dev/integration_tests/flutter_gallery/windows/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(flutter_gallery LANGUAGES CXX)
 
 set(BINARY_NAME "flutter_gallery")
diff --git a/dev/integration_tests/flutter_gallery/windows/flutter/CMakeLists.txt b/dev/integration_tests/flutter_gallery/windows/flutter/CMakeLists.txt
index b02c548..b2e4bd8 100644
--- a/dev/integration_tests/flutter_gallery/windows/flutter/CMakeLists.txt
+++ b/dev/integration_tests/flutter_gallery/windows/flutter/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
 
diff --git a/dev/integration_tests/flutter_gallery/windows/runner/CMakeLists.txt b/dev/integration_tests/flutter_gallery/windows/runner/CMakeLists.txt
index 0b899a0..de2d891 100644
--- a/dev/integration_tests/flutter_gallery/windows/runner/CMakeLists.txt
+++ b/dev/integration_tests/flutter_gallery/windows/runner/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(runner LANGUAGES CXX)
 
 add_executable(${BINARY_NAME} WIN32
diff --git a/dev/manual_tests/windows/CMakeLists.txt b/dev/manual_tests/windows/CMakeLists.txt
index 79b299c..af381b9 100644
--- a/dev/manual_tests/windows/CMakeLists.txt
+++ b/dev/manual_tests/windows/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(manual_tests LANGUAGES CXX)
 
 set(BINARY_NAME "manual_tests")
diff --git a/dev/manual_tests/windows/flutter/CMakeLists.txt b/dev/manual_tests/windows/flutter/CMakeLists.txt
index 744f08a..66188df 100644
--- a/dev/manual_tests/windows/flutter/CMakeLists.txt
+++ b/dev/manual_tests/windows/flutter/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
 
diff --git a/dev/manual_tests/windows/runner/CMakeLists.txt b/dev/manual_tests/windows/runner/CMakeLists.txt
index 977e38b..72cf6b8 100644
--- a/dev/manual_tests/windows/runner/CMakeLists.txt
+++ b/dev/manual_tests/windows/runner/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(runner LANGUAGES CXX)
 
 add_executable(${BINARY_NAME} WIN32
diff --git a/examples/api/windows/CMakeLists.txt b/examples/api/windows/CMakeLists.txt
index 7dfd4a7..56a9a60 100644
--- a/examples/api/windows/CMakeLists.txt
+++ b/examples/api/windows/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(dartpad_curve2_d_0 LANGUAGES CXX)
 
 set(BINARY_NAME "dartpad_curve2_d_0")
diff --git a/examples/api/windows/flutter/CMakeLists.txt b/examples/api/windows/flutter/CMakeLists.txt
index b02c548..b2e4bd8 100644
--- a/examples/api/windows/flutter/CMakeLists.txt
+++ b/examples/api/windows/flutter/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
 
diff --git a/examples/api/windows/runner/CMakeLists.txt b/examples/api/windows/runner/CMakeLists.txt
index 0b899a0..de2d891 100644
--- a/examples/api/windows/runner/CMakeLists.txt
+++ b/examples/api/windows/runner/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(runner LANGUAGES CXX)
 
 add_executable(${BINARY_NAME} WIN32
diff --git a/packages/flutter_tools/lib/src/windows/build_windows.dart b/packages/flutter_tools/lib/src/windows/build_windows.dart
index 5a87af2..f1be5b3 100644
--- a/packages/flutter_tools/lib/src/windows/build_windows.dart
+++ b/packages/flutter_tools/lib/src/windows/build_windows.dart
@@ -22,7 +22,7 @@
 import 'install_manifest.dart';
 import 'visual_studio.dart';
 
-// From https://cmake.org/cmake/help/v3.15/manual/cmake-generators.7.html#visual-studio-generators
+// From https://cmake.org/cmake/help/v3.14/manual/cmake-generators.7.html#visual-studio-generators
 // This may need to become a getter on VisualStudio in the future to support
 // future major versions of Visual Studio.
 const String _cmakeVisualStudioGeneratorIdentifier = 'Visual Studio 16 2019';
diff --git a/packages/flutter_tools/templates/app_shared/windows.tmpl/CMakeLists.txt.tmpl b/packages/flutter_tools/templates/app_shared/windows.tmpl/CMakeLists.txt.tmpl
index 7c0065f..d969f43 100644
--- a/packages/flutter_tools/templates/app_shared/windows.tmpl/CMakeLists.txt.tmpl
+++ b/packages/flutter_tools/templates/app_shared/windows.tmpl/CMakeLists.txt.tmpl
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project({{projectName}} LANGUAGES CXX)
 
 set(BINARY_NAME "{{projectName}}")
diff --git a/packages/flutter_tools/templates/app_shared/windows.tmpl/flutter/CMakeLists.txt b/packages/flutter_tools/templates/app_shared/windows.tmpl/flutter/CMakeLists.txt
index b02c548..b2e4bd8 100644
--- a/packages/flutter_tools/templates/app_shared/windows.tmpl/flutter/CMakeLists.txt
+++ b/packages/flutter_tools/templates/app_shared/windows.tmpl/flutter/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
 
diff --git a/packages/flutter_tools/templates/app_shared/windows.tmpl/runner/CMakeLists.txt b/packages/flutter_tools/templates/app_shared/windows.tmpl/runner/CMakeLists.txt
index 0b899a0..de2d891 100644
--- a/packages/flutter_tools/templates/app_shared/windows.tmpl/runner/CMakeLists.txt
+++ b/packages/flutter_tools/templates/app_shared/windows.tmpl/runner/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 project(runner LANGUAGES CXX)
 
 add_executable(${BINARY_NAME} WIN32
diff --git a/packages/flutter_tools/templates/plugin/windows.tmpl/CMakeLists.txt.tmpl b/packages/flutter_tools/templates/plugin/windows.tmpl/CMakeLists.txt.tmpl
index 149d3ad..5d7b0ef 100644
--- a/packages/flutter_tools/templates/plugin/windows.tmpl/CMakeLists.txt.tmpl
+++ b/packages/flutter_tools/templates/plugin/windows.tmpl/CMakeLists.txt.tmpl
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.14)
 set(PROJECT_NAME "{{projectName}}")
 project(${PROJECT_NAME} LANGUAGES CXX)