ENH: Expose ios deployment target in CMake config

Can not use `CMAKE_OSX_DEPLOYMENT_TARGET` because it will set the
minimum version for macosx and not iphoneos or ios-simulator. Issue filed
in CMake: cmake/cmake#17431

Instead, update the proper flags in the toolchain files by passing the
`IOS_DEVELOPMENT_TARGET` during configuration.

Default `IOS_DEVELOPMENT_TARGET` to the current sdk version (latest). It
used to default to ios 5.0 for the simulators (2011) and ios 8.0 for the
devices (2014).

CMake/ios.device.toolchain.cmake.in

@@ -31,8 +31,8 @@ execute_process(COMMAND /usr/bin/xcrun -sdk iphoneos --show-sdk-path
 
 # Set compilation flags
 set(CMAKE_OSX_ARCHITECTURES @CMAKE_CC_ARCH@)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -miphoneos-version-min=8.0 -fvisibility=hidden -fvisibility-inlines-hidden")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -miphoneos-version-min=8.0 -fvisibility=hidden -fvisibility-inlines-hidden")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -miphoneos-version-min=@IOS_DEPLOYMENT_TARGET@ -fvisibility=hidden -fvisibility-inlines-hidden")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -miphoneos-version-min=@IOS_DEPLOYMENT_TARGET@ -fvisibility=hidden -fvisibility-inlines-hidden")
 
 # Embed bitcode, if requested
 if (@IOS_EMBED_BITCODE@)

CMake/ios.simulator.toolchain.cmake.in

@@ -22,21 +22,10 @@ execute_process(COMMAND /usr/bin/xcrun -sdk iphonesimulator --show-sdk-path
                 OUTPUT_VARIABLE CMAKE_OSX_SYSROOT
                 OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-# If the we are on 7.0 or higher SDK we should add simulator version min to get
-# things to compile.  This is probably more properly handled with a compiler version
-# check but this works for now.
-if(CMAKE_OSX_SYSROOT MATCHES iPhoneSimulator[7-9].[0-9].sdk)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mios-simulator-version-min=5.0")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mios-simulator-version-min=5.0")
-else()
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D__IPHONE_OS_VERSION_MIN_REQUIRED=50000")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D__PHONE_OS_VERSION_MIN_REQIORED=50000")
-endif()
-
 # Set compilation flags
 set(CMAKE_OSX_ARCHITECTURES @IOS_SIMULATOR_ARCHITECTURES@)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden -fvisibility-inlines-hidden")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -fvisibility-inlines-hidden")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mios-simulator-version-min=@IOS_DEPLOYMENT_TARGET@ -fvisibility=hidden -fvisibility-inlines-hidden")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mios-simulator-version-min=@IOS_DEPLOYMENT_TARGET@ -fvisibility=hidden -fvisibility-inlines-hidden")
 
 set(CMAKE_OSX_ARCHITECTURES "${CMAKE_OSX_ARCHITECTURES}" CACHE STRING "osx architectures")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}" CACHE STRING "c++ flags")

CMake/vtkiOS.cmake

@@ -26,6 +26,12 @@ if(NOT ${IOS_ARCHS_NBR})
   message(FATAL_ERROR "No IOS simulator or device architecture to compile for. Populate IOS_DEVICE_ARCHITECTURES and/or IOS_SIMULATOR_ARCHITECTURES.")
 endif()
 
+# iOS Deployment Target
+execute_process(COMMAND /usr/bin/xcrun -sdk iphoneos --show-sdk-version
+                OUTPUT_VARIABLE IOS_DEPLOYMENT_TARGET_TMP
+                OUTPUT_STRIP_TRAILING_WHITESPACE)
+set(IOS_DEPLOYMENT_TARGET ${IOS_DEPLOYMENT_TARGET_TMP} CACHE STRING "iOS Deployment Target")
+
 set(IOS_EMBED_BITCODE ON CACHE BOOL "Embed LLVM bitcode")
 
 set(CMAKE_FRAMEWORK_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}/frameworks"