build: cleanup swiftCore link definition

Colocate the target specific library specification.  Inline the single
site use of the place holder ICU_UC and ICU_I18N libraries rather than
trying to create special library processing code for that.

Author: compnerd

cmake/modules/AddSwift.cmake

@@ -1861,24 +1861,7 @@ function(add_swift_target_library name)
       endif()
 
       foreach(lib ${SWIFTLIB_PRIVATE_LINK_LIBRARIES})
-        if("${lib}" STREQUAL "ICU_UC")
-          list(APPEND swiftlib_private_link_libraries_targets
-               "${SWIFT_${sdk}_${arch}_ICU_UC}")
-          # temporary fix for atomic needing to be
-          # after object files for libswiftCore.so
-          if("${sdk}" STREQUAL "ANDROID")
-            list(APPEND swiftlib_private_link_libraries_targets
-                 "-latomic")
-          # the same issue on FreeBSD, missing symbols:
-          # __atomic_store, __atomic_compare_exchange, __atomic_load
-          elseif("${sdk}" STREQUAL "FREEBSD")
-            list(APPEND swiftlib_private_link_libraries_targets
-                 "${SWIFTLIB_DIR}/clang/lib/freebsd/libclang_rt.builtins-${arch}.a")
-          endif()
-        elseif("${lib}" STREQUAL "ICU_I18N")
-          list(APPEND swiftlib_private_link_libraries_targets
-               "${SWIFT_${sdk}_${arch}_ICU_I18N}")
-        elseif(TARGET "${lib}${VARIANT_SUFFIX}")
+        if(TARGET "${lib}${VARIANT_SUFFIX}")
           list(APPEND swiftlib_private_link_libraries_targets
               "${lib}${VARIANT_SUFFIX}")
         else()

stdlib/public/core/CMakeLists.txt

@@ -238,21 +238,33 @@ else()
   #set(LINK_FLAGS
   #  -Wl,--whole-archive swiftRuntime -Wl,--no-whole-archive)
   if("${SWIFT_PATH_TO_LIBICU_BUILD}" STREQUAL "")
-    list(APPEND swift_core_private_link_libraries ICU_UC ICU_I18N)
+    list(APPEND swift_core_private_link_libraries
+      ${SWIFT_${SWIFT_PRIMARY_VARIANT_SDK}_${SWIFT_PRIMARY_VARIANT_ARCH}_ICU_UC}
+      ${SWIFT_${SWIFT_PRIMARY_VARIANT_SDK}_${SWIFT_PRIMARY_VARIANT_ARCH}_ICU_I18N})
   else()
     list(APPEND swift_core_private_link_libraries -licui18nswift -licuucswift -licudataswift)
   endif()
 endif()
 
-if("${CMAKE_SYSTEM_NAME}" STREQUAL "CYGWIN")
+if(SWIFT_PRIMARY_VARIANT_SDK STREQUAL ANDROID)
+  # workaround for libatomic needing to be after object files for swiftCore.so
+  list(APPEND swift_core_private_link_libraries atomic)
+elseif(SWIFT_PRIMARY_VARIANT_SDK STREQUAL CYGWIN)
   # TODO(compnerd) cache this variable to permit re-configuration
   execute_process(COMMAND "cygpath" "-u" "$ENV{SYSTEMROOT}" OUTPUT_VARIABLE ENV_SYSTEMROOT)
   list(APPEND swift_core_private_link_libraries "${ENV_SYSTEMROOT}/system32/psapi.dll")
-endif()
-
-if(SWIFT_PRIMARY_VARIANT_SDK STREQUAL FREEBSD)
+elseif(SWIFT_PRIMARY_VARIANT_SDK STREQUAL FREEBSD)
   find_library(EXECINFO_LIBRARY execinfo)
   list(APPEND swift_core_private_link_libraries ${EXECINFO_LIBRARY})
+  # workaround for libatomic needing to be after object files for swiftCore.so
+  list(APPEND swift_core_private_link_libraries
+    ${SWIFTLIB_DIR}/clang/lib/freebsd/libclang_rt.builtins-${SWIFT_PRIMARY_VARIANT_ARCH}.a)
+elseif(SWIFT_PRIMARY_VARIANT_SDK STREQUAL LINUX)
+  if(SWIFT_BUILD_STATIC_STDLIB)
+    list(APPEND swift_core_private_link_libraries swiftImageInspectionShared)
+  endif()
+elseif(SWIFT_PRIMARY_VARIANT_SDK STREQUAL WINDOWS)
+  list(APPEND swift_core_private_link_libraries shell32)
 endif()
 
 option(SWIFT_CHECK_ESSENTIAL_STDLIB
@@ -275,15 +287,6 @@ if(SWIFT_CHECK_ESSENTIAL_STDLIB)
   target_link_libraries(swift_stdlib_essential ${RUNTIME_DEPENDENCY})
 endif()
 
-
-if(SWIFT_BUILD_STATIC_STDLIB AND "${SWIFT_PRIMARY_VARIANT_SDK}" STREQUAL "LINUX")
-   list(APPEND swift_core_private_link_libraries swiftImageInspectionShared)
-endif()
-
-if(SWIFT_PRIMARY_VARIANT_SDK STREQUAL WINDOWS)
-  list(APPEND swift_core_private_link_libraries shell32)
-endif()
-
 add_swift_target_library(swiftCore
                   ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB IS_STDLIB_CORE
                     ${SWIFTLIB_SOURCES}