Add TargetConditionals.h

I added it before, but made a mistake so the file in the include
directory was an empty file.

Author: aykevl

Diff for: src/usr/include/TargetConditionals.h

@@ -0,0 +1,33 @@
+// This file is placed in the public domain.
+//
+// This file is a replacement for TargetConditionals.h for which I can't find an
+// open source version in an open source Apple library. (There is one in
+// CarbonHeaders but it is outdated doesn't support ARM64).
+
+#define TARGET_CPU_PPC          0
+#define TARGET_CPU_PPC64        0
+#define TARGET_CPU_68K          0
+#define TARGET_CPU_X86          0
+#define TARGET_CPU_X86_64       defined(__x86_64__)
+#define TARGET_CPU_ARM          0
+#define TARGET_CPU_ARM64        defined(__arm64__)
+#define TARGET_CPU_MIPS         0
+#define TARGET_CPU_SPARC        0
+#define TARGET_CPU_ALPHA        0
+
+// We only support macOS (OSX) right now.
+#define TARGET_OS_WIN32       0
+#define TARGET_OS_WINDOWS     0
+#define TARGET_OS_UNIX        0
+#define TARGET_OS_LINUX       0
+#define TARGET_OS_MAC         1
+#define TARGET_OS_OSX         1
+#define TARGET_OS_IPHONE      0
+#define TARGET_OS_IOS         0
+#define TARGET_OS_MACCATALYST 0
+#define TARGET_OS_TV          0
+#define TARGET_OS_WATCH       0
+#define TARGET_OS_VISION      0
+#define TARGET_OS_BRIDGE      0
+#define TARGET_OS_SIMULATOR   0
+#define TARGET_OS_DRIVERKIT   0

Diff for: update.sh

@@ -202,11 +202,6 @@ cp -p src/signal.h $include/machine/signal.h
 cp -p src/availability.h $include/os/availability.h
 cp -p src/TargetConditionals.h $include/TargetConditionals.h
 
-# This was previously a file from CarbonHeaders, but it was very old (didn't
-# include support for arm64) so failed to compile. An empty file seems to be
-# sufficient for now.
-printf "" > $include/TargetConditionals.h
-
 # Replace machine/_types.h, arm/_types.h, and i386/_types.h with a single file.
 # Do forward includes though, because arm/types.h and i386/types.h still
 # include the */_types.h version.