[lto][cmake] Do not access SWIFT_TOOLS_ENABLE_LTO directly in _add_variant_{c_compile,variant_link}_flags. Pass it in as an arg instead.

This will allow control on the outside of these calls on whether or not LTO is
enabled. This is necessary for turning off LTO on target libraries.

rdar://24717107

Author: gottesmm

cmake/modules/AddSwift.cmake

@@ -117,7 +117,7 @@ function(_add_variant_c_compile_link_flags)
 endfunction()
 
 function(_add_variant_c_compile_flags)
-  set(oneValueArgs SDK ARCH BUILD_TYPE ENABLE_ASSERTIONS ANALYZE_CODE_COVERAGE DEPLOYMENT_VERSION_IOS RESULT_VAR_NAME)
+  set(oneValueArgs SDK ARCH BUILD_TYPE ENABLE_ASSERTIONS ANALYZE_CODE_COVERAGE DEPLOYMENT_VERSION_IOS RESULT_VAR_NAME ENABLE_LTO)
   cmake_parse_arguments(CFLAGS
     ""
     "${oneValueArgs}"
@@ -131,7 +131,7 @@ function(_add_variant_c_compile_flags)
     ARCH "${CFLAGS_ARCH}"
     BUILD_TYPE "${CFLAGS_BUILD_TYPE}"
     ENABLE_ASSERTIONS "${CFLAGS_ENABLE_ASSERTIONS}"
-    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
+    ENABLE_LTO "${CFLAGS_ENABLE_LTO}"
     ANALYZE_CODE_COVERAGE FALSE
     DEPLOYMENT_VERSION_IOS "${CFLAGS_DEPLOYMENT_VERSION_IOS}"
     RESULT_VAR_NAME result)
@@ -214,7 +214,7 @@ function(_add_variant_swift_compile_flags
 endfunction()
 
 function(_add_variant_link_flags)
-  set(oneValueArgs SDK ARCH BUILD_TYPE ENABLE_ASSERTIONS ANALYZE_CODE_COVERAGE DEPLOYMENT_VERSION_IOS RESULT_VAR_NAME)
+  set(oneValueArgs SDK ARCH BUILD_TYPE ENABLE_ASSERTIONS ANALYZE_CODE_COVERAGE DEPLOYMENT_VERSION_IOS RESULT_VAR_NAME ENABLE_LTO)
   cmake_parse_arguments(LFLAGS
     ""
     "${oneValueArgs}"
@@ -236,7 +236,7 @@ function(_add_variant_link_flags)
     ARCH "${LFLAGS_ARCH}"
     BUILD_TYPE "${LFLAGS_BUILD_TYPE}"
     ENABLE_ASSERTIONS "${LFLAGS_ENABLE_ASSERTIONS}"
-    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
+    ENABLE_LTO "${LFLAGS_ENABLE_LTO}"
     ANALYZE_CODE_COVERAGE "${LFLAGS_ANALYZE_CODE_COVERAGE}"
     DEPLOYMENT_VERSION_IOS "${LFLAGS_DEPLOYMENT_VERSION_IOS}"
     RESULT_VAR_NAME result)
@@ -803,6 +803,7 @@ function(_add_swift_library_single target name)
     BUILD_TYPE "${build_type}"
     ENABLE_ASSERTIONS "${enable_assertions}"
     ANALYZE_CODE_COVERAGE "${analyze_code_coverage}"
+    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
     DEPLOYMENT_VERSION_IOS "${SWIFTLIB_DEPLOYMENT_VERSION_IOS}"
     RESULT_VAR_NAME c_compile_flags
     )
@@ -812,6 +813,7 @@ function(_add_swift_library_single target name)
     BUILD_TYPE "${build_type}"
     ENABLE_ASSERTIONS "${enable_assertions}"
     ANALYZE_CODE_COVERAGE "${analyze_code_coverage}"
+    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
     DEPLOYMENT_VERSION_IOS "${SWIFTLIB_DEPLOYMENT_VERSION_IOS}"
     RESULT_VAR_NAME link_flags
       )
@@ -1415,13 +1417,15 @@ function(_add_swift_executable_single name)
     ARCH "${SWIFTEXE_SINGLE_ARCHITECTURE}"
     BUILD_TYPE "${CMAKE_BUILD_TYPE}"
     ENABLE_ASSERTIONS "${LLVM_ENABLE_ASSERTIONS}"
+    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
     ANALYZE_CODE_COVERAGE "${SWIFT_ANALYZE_CODE_COVERAGE}"
     RESULT_VAR_NAME c_compile_flags)
   _add_variant_link_flags(
     SDK "${SWIFTEXE_SINGLE_SDK}"
     ARCH "${SWIFTEXE_SINGLE_ARCHITECTURE}"
     BUILD_TYPE "${CMAKE_BUILD_TYPE}"
     ENABLE_ASSERTIONS "${LLVM_ENABLE_ASSERTIONS}"
+    ENABLE_LTO "${SWIFT_TOOLS_ENABLE_LTO}"
     ANALYZE_CODE_COVERAGE "${SWIFT_ANALYZE_CODE_COVERAGE}"
     RESULT_VAR_NAME link_flags)