Add architecture specific target option macros

These macros are defined in target.hpp. This commit adds the macros:

NOINLINE - Never inline the function
ALWAYS_INLINE - Force the function to be inlined (also adds the inline
attribute to the function)

TARGET_ARM_MODE - Compile all future functions in ARM mode until
TARGET_END_MODE is reached. No-op if not compiling for ARM.
TARGET_THUMB_MODE - Compile all future functions in thumb mode until
TARGET_END_MODE is reached. No-op if not compiling for ARM.
TARGET_END_MODE - Undo the last TARGET_*_MODE option.

ARM_MODE - Compile this function in ARM mode.
THUMB_MODE - Compile this function in thumb mode.

include/mtl/target.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#ifndef __GNUC__
+#error Failed to create target macros. Compiler is not GCC.
+#endif
+
+#define NOINLINE [[gnu::noinline]]
+#define ALWAYS_INLINE [[gnu::always_inline]] inline
+
+#ifdef __arm__
+
+#define TARGET_ARM_MODE _Pragma("GCC push_options") _Pragma("GCC target(\"arm\")")
+#define TARGET_THUMB_MODE _Pragma("GCC push_options") _Pragma("GCC target(\"thumb\")")
+#define TARGET_END_MODE _Pragma("GCC pop_options")
+#define ARM_MODE [[gnu::target("arm")]]
+#define THUMB_MODE [[gnu::target("thumb")]]
+
+#else
+
+#define TARGET_ARM_MODE
+#define TARGET_THUMB_MODE
+#define TARGET_END_MODE
+#define ARM_MODE
+#define THUMB_MODE
+
+#endif
+