Cannot compile Foundation on ARM

<module-includes>:1:10: note: in file included from <module-includes>:1:
#include "CoreFoundation.h"
         ^
/home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CoreFoundation.h:58:10: note: in file included from /home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CoreFoundation.h:58:
#include <CoreFoundation/CFCalendar.h>
         ^
/home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CFCalendar.h:21:10: note: in file included from /home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CFCalendar.h:21:
#include <CoreFoundation/CFTimeZone.h>
         ^
/home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CFTimeZone.h:23:10: note: in file included from /home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CFTimeZone.h:23:
#include <CoreFoundation/CFString.h>
         ^
/home/ryan/Source/swift-corelibs-foundation/../build/Ninja-ReleaseAssert/foundation-linux-armv7/Foundation/usr/lib/swift/CoreFoundation/CFString.h:265:123: error: reference to 'va_list' is ambiguous
CFStringRef CFStringCreateWithFormatAndArguments(CFAllocatorRef alloc, CFDictionaryRef formatOptions, CFStringRef format, va_list arguments) CF_FORMAT_FUNCTION(3,0);
                                                                                                                          ^
/home/ryan/Source/build/Ninja-ReleaseAssert/swift-linux-armv7/lib/swift/clang/include/stdarg.h:30:27: note: candidate found by name lookup is 'va_list'
typedef __builtin_va_list va_list;
                          ^
/usr/include/stdio.h:79:20: note: candidate found by name lookup is 'va_list'
typedef _G_va_list va_list;