build: Xcode build improvements

* Use RelWithDebInfo as the launch configuration in the default scheme

* Assume IPO is supported under Xcode, since checking takes over 10 seconds for some reason

cmake/common/compiler_common.cmake

@@ -9,7 +9,13 @@ include(CheckIPOSupported)
 option(ENABLE_IPO "Enable interprocedural optimization (LTO)" YES)
 message(STATUS "Checking if interprocedural optimization is supported")
 if(ENABLE_IPO)
-  check_ipo_supported(RESULT ipo_supported OUTPUT output)
+  # Checking IPO support takes an inordinately long time under the Xcode generator; under Xcode, just assume that
+  # IPO is supported.
+  if(NOT XCODE)
+    check_ipo_supported(RESULT ipo_supported OUTPUT output)
+  else()
+    set(ipo_supported YES)
+  endif()
   if(ipo_supported)
     set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)
     set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO TRUE)

cmake/macos/xcode.cmake

@@ -90,6 +90,9 @@ set(CMAKE_XCODE_ATTRIBUTE_CLANG_MODULES_AUTOLINK NO)
 # Enable strict msg_send rules for ObjC
 set(CMAKE_XCODE_ATTRIBUTE_ENABLE_STRICT_OBJC_MSGSEND YES)
 
+# Use RelWithDebInfo as the launch configuration in the default scheme
+set(CMAKE_XCODE_SCHEME_LAUNCH_CONFIGURATION RelWithDebInfo)
+
 # Set default warnings for all languages
 set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING YES)
 set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_BOOL_CONVERSION YES)