Add ARM/thumb pragma target

Add ARM/thumb pragma target

	PR target/52144
	* config/arm/arm-c.c (arm_cpu_cpp_builtins): Conditionally define
	 macros in ...
	(arm_cpu_builtins): New function.
	(arm_pragma_target_parse): Call arm_cpu_builtins.
	* config/arm/arm-protos.h (arm_cpu_builtins): Declare.
	(arm_register_target_pragmas): Likewise.
	* config/arm/arm.h (REGISTER_TARGET_PRAGMAS):
	 Call arm_register_target_pragmas.
	* config/arm/arm-c.c (arm_register_target_pragmas): New function.
	(arm_pragma_target_parse): Likewise.

	PR target/52144
	* gcc.target/arm/pragma_attribute.c: New test.

From-SVN: r224365