build: Apply XCode 8 workaround for iOS too

clock_gettime was also added for iOS 10.0, so don't use it if we're
targetting an older version. That would've caused the symbol to not be
found at runtime on older devices.

configure.ac

@@ -693,14 +693,21 @@ AC_CHECK_FUNC(clock_gettime, [CLOCK_GETTIME_FOUND="yes"], [
 # autoconf check does its own prototype declaration that doesn't trigger that
 # compiler flag.
 #
-# It's only starting from macOS 10.12, that clock_gettime is actually available,
-# so we can unconditionally disable it when targetting older versions.
+# It's only starting from macOS 10.12 and iOS 10.0 that clock_gettime is
+# actually available, so we can unconditionally disable it for older versions.
 case "$host_os" in
   darwin*)
     AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 #include <AvailabilityMacros.h>
-#if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
-#error "Not compiling for OS X 10.12 or later"
+#include <TargetConditionals.h>
+#if defined(TARGET_OS_MAC)
+#  if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
+#    error "Not compiling for OS X 10.12 or later"
+#  endif
+#else
+#  if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_10_0
+#    error "Not compiling for iOS 10.0 or later"
+#  endif
 #endif
     ]])], [], [
     if test "$CLOCK_GETTIME_FOUND" = "yes"; then

meson.build

@@ -185,24 +185,32 @@ if cc.has_function('getpagesize', prefix : '#include<unistd.h>')
   cdata.set('HAVE_GETPAGESIZE', 1)
 endif
 
-# With OS X 10.11.6 and XCode 8, clock_gettime will be incorrectly detected as
-# being available because the symbol is available in the .tbd file as a weak
-# symbol. See: https://github.com/Homebrew/homebrew-core/issues/3727#issue-170086273
+# With XCode 8, clock_gettime will be incorrectly detected as being available
+# regardless of what version of OS X you target because the symbol is available
+# in the .tbd file as a weak symbol.
+# See: https://bugzilla.gnome.org/show_bug.cgi?id=772451 
 #
 # We cannot simply do cc.has_function with -Wl,-no_weak_imports because the
 # check does its own prototype decl that doesn't trigger that compiler flag.
 #
-# It's only starting from macOS 10.12, that clock_gettime is actually available,
-# so we can unconditionally disable it for older versions.
-for_osx_10_12_src = '''#include <AvailabilityMacros.h>
-#if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
-#error "Not compiling for OS X 10.12 or later"
+# It's only starting from macOS 10.12 and iOS 10.0 that clock_gettime is
+# actually available, so we can unconditionally disable it for older versions.
+disable_clock_gettime_src = '''#include <AvailabilityMacros.h>
+#include <TargetConditionals.h>
+#if defined(TARGET_OS_MAC)
+#  if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
+#    error "Not compiling for OS X 10.12 or later"
+#  endif
+#else
+#  if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_10_0
+#    error "Not compiling for iOS 10.0 or later"
+#  endif
 #endif
 '''
 
 if cc.has_function('clock_gettime', prefix : '#include <time.h>')
   if host_machine.system() == 'darwin'
-    if cc.compiles(for_osx_10_12_src, name : 'minimum OS X version required >= 10.12')
+    if cc.compiles(disable_clock_gettime_src, name : 'target darwin/ios version has clock_gettime')
       cdata.set('HAVE_CLOCK_GETTIME', 1)
     endif
   else