[ios, macos] Enable link-time optimization for iOS release builds (#12502)

cmake/loop-darwin.cmake

@@ -13,4 +13,6 @@ create_source_groups(mbgl-loop-darwin)
 
 set_target_properties(mbgl-loop-darwin PROPERTIES FOLDER "Core")
 
+initialize_xcode_cxx_build_settings(mbgl-loop-darwin)
+
 xcode_create_scheme(TARGET mbgl-loop-darwin)

cmake/mbgl.cmake

@@ -203,6 +203,9 @@ macro(initialize_xcode_cxx_build_settings target)
 
     # -Wrange-loop-analysis
     set_xcode_property(${target} CLANG_WARN_RANGE_LOOP_ANALYSIS YES)
+
+    # -flto
+    set_xcode_property(${target} LLVM_LTO $<$<OR:$<CONFIG:Release>,$<CONFIG:RelWithDebugInfo>>:YES>)
 endmacro(initialize_xcode_cxx_build_settings)
 
 # CMake 3.1 does not have this yet.

cmake/offline.cmake

@@ -21,6 +21,8 @@ mbgl_platform_offline()
 
 create_source_groups(mbgl-offline)
 
+initialize_xcode_cxx_build_settings(mbgl-offline)
+
 set_target_properties(mbgl-offline PROPERTIES FOLDER "Executables")
 
 xcode_create_scheme(

platform/ios/ios.xcodeproj/project.pbxproj

@@ -3793,6 +3793,7 @@
 				INFOPLIST_FILE = framework/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
+				LLVM_LTO = YES;
 				OTHER_CFLAGS = "-fvisibility=hidden";
 				OTHER_CPLUSPLUSFLAGS = (
 					"$(OTHER_CFLAGS)",
@@ -3878,6 +3879,7 @@
 					"$(mbgl_core_INCLUDE_DIRECTORIES)",
 					"$(mbgl_filesource_LINK_LIBRARIES)",
 				);
+				LLVM_LTO = YES;
 				OTHER_CFLAGS = "-fvisibility=hidden";
 				OTHER_CPLUSPLUSFLAGS = (
 					"$(OTHER_CFLAGS)",

platform/macos/macos.xcodeproj/project.pbxproj

@@ -2004,6 +2004,7 @@
 				INFOPLIST_FILE = "$(SRCROOT)/sdk/Info.plist";
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/Frameworks";
+				LLVM_LTO = YES;
 				OTHER_CFLAGS = "-fvisibility=hidden";
 				OTHER_LDFLAGS = (
 					"$(mbgl_core_LINK_LIBRARIES)",