Bump CMake version to 3.19.6.

Updates the CMake version for Swift and the Swift Benchmarks to 3.19.6.
Updates the docs to reflect this change. Does not modify the required version for building the stdlib.

Author: zoecarver

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.12.4)
+cmake_minimum_required(VERSION 3.19.6)
 
 # TODO: Fix RPATH usage to be CMP0068 compliant
 # Disable Policy CMP0068 for CMake 3.9
@@ -183,7 +183,7 @@ endif()
 set(SWIFT_USE_LINKER ${SWIFT_USE_LINKER_default} CACHE STRING
     "Build Swift with a non-default linker")
 
-option(SWIFT_DISABLE_DEAD_STRIPPING 
+option(SWIFT_DISABLE_DEAD_STRIPPING
       "Turn off Darwin-specific dead stripping for Swift host tools." FALSE)
 
 set(SWIFT_TOOLS_ENABLE_LTO OFF CACHE STRING "Build Swift tools with LTO. One

benchmark/CMakeLists.txt

@@ -1,6 +1,6 @@
 # -*- mode: cmake -*-
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.19.6)
 
 # Add path for custom CMake modules.
 list(APPEND CMAKE_MODULE_PATH

benchmark/README.md

@@ -43,7 +43,7 @@ library should be distributed alongside them.
 ### CMake Standalone (no build-script)
 
 To build the Swift benchmarks using only an Xcode installation: install an
-Xcode version with Swift support, install cmake 2.8.12, and ensure Xcode is
+Xcode version with Swift support, install cmake 3.19.6 or higher, and ensure Xcode is
 selected with xcode-select.
 
 The following build options are available:

docs/HowToGuides/GettingStarted.md

@@ -158,7 +158,7 @@ Double-check that running `pwd` prints a path ending with `swift`.
    * [CentOS 7](https://github.com/apple/swift-docker/blob/main/swift-ci/master/centos/7/Dockerfile)
    * [CentOS 8](https://github.com/apple/swift-docker/blob/main/swift-ci/master/centos/8/Dockerfile)
    * [Amazon Linux 2](https://github.com/apple/swift-docker/blob/main/swift-ci/master/amazon-linux/2/Dockerfile)
-   
+
 2. To install sccache (optional):
    ```
    sudo snap install sccache --candidate --classic
@@ -170,7 +170,7 @@ Double-check that running `pwd` prints a path ending with `swift`.
 
 ### Spot check dependencies
 
-* Run `cmake --version`: This should be 3.18.1 or higher for macOS.
+* Run `cmake --version`: This should be 3.19.6 or higher.
 * Run `python3 --version`: Check that this succeeds.
 * Run `ninja --version`: Check that this succeeds.
 * Run `sccache --version`: Check that this succeeds.