build: simplify the build rules with newer CMake (NFC)

Swift now requires CMake 3.19.6 as a minimum version.  Assume that we
can use CMake newer than 3.16 and simplify the build rules.

Author: compnerd

CMakeLists.txt

@@ -1,24 +1,12 @@
-cmake_minimum_required(VERSION 3.15.1)
+cmake_minimum_required(VERSION 3.19)
 
 project(SwiftTSC LANGUAGES C Swift)
 
-set(SWIFT_VERSION 5)
-set(CMAKE_Swift_LANGUAGE_VERSION ${SWIFT_VERSION})
-if(CMAKE_VERSION VERSION_LESS 3.16)
-    add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-swift-version$<SEMICOLON>${SWIFT_VERSION}>)
-    # Workaround for CMake 3.15 which doesn't link libraries properly on Windows
-    set(CMAKE_LINK_LIBRARY_FLAG "-l")
-endif()
-
+set(CMAKE_Swift_LANGUAGE_VERSION 5)
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
-if(CMAKE_VERSION VERSION_LESS 3.16 AND CMAKE_SYSTEM_NAME STREQUAL Windows)
-  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-else()
-  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-endif()
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 
 set(CMAKE_DISABLE_IN_SOURCE_BUILD YES)