build: simplify the build rules (NFC)

The minimum version of CMake is set to 3.19.6.  Remove the workarounds
for the older releases of CMake allowing us to simplify the build rules.

Author: compnerd

CMakeLists.txt

@@ -12,44 +12,19 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules)
 
 project(SwiftDriver 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>${SWIFT_VERSION}>)
-    set(CMAKE_LINK_LIBRARY_FLAG "-l")
-endif()
-
-# ensure Swift compiler can find _CSwiftScan
-add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-I$<SEMICOLON>${CMAKE_CURRENT_SOURCE_DIR}/Sources/CSwiftScan/include>)
-
+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)
 
-option(BUILD_SHARED_LIBS "Build shared libraries by default" YES)
-
 set(CMAKE_MACOSX_RPATH YES)
-if(CMAKE_VERSION VERSION_LESS 3.17)
-  if(NOT CMAKE_SYSTEM_NAME STREQUAL Windows)
-    set(CMAKE_EXECUTABLE_RUNTIME_Swift_FLAG "-Xlinker -rpath -Xlinker ")
-    set(CMAKE_SHARED_LIBRARY_RUNTIME_Swift_FLAG "-Xlinker -rpath -Xlinker ")
 
-    if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
-      set(CMAKE_EXECUTABLE_RUNTIME_Swift_FLAG_SEP "")
-      set(CMAKE_SHARED_LIBRARY_RUNTIME_Swift_FLAG_SEP "")
-    else()
-      set(CMAKE_EXECUTABLE_RUNTIME_Swift_FLAG_SEP ":")
-      set(CMAKE_SHARED_LIBRARY_RUNTIME_Swift_FLAG_SEP ":")
-    endif()
-  endif()
-endif()
+# ensure Swift compiler can find _CSwiftScan
+add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-I$<SEMICOLON>${CMAKE_CURRENT_SOURCE_DIR}/Sources/CSwiftScan/include>)
+
+option(BUILD_SHARED_LIBS "Build shared libraries by default" YES)
 
 find_package(TSC CONFIG REQUIRED)