Remove __gnu_inline function attribute

Fixes #18

debugbreak.h

@@ -1,4 +1,4 @@
-/* Copyright (c) 2011-2018, Scott Tsai
+/* Copyright (c) 2011-2021, Scott Tsai
  * 
  * All rights reserved.
  * 
@@ -49,7 +49,7 @@ __inline__ static void trap_instruction(void)
 #elif defined(__thumb__)
 	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
 /* FIXME: handle __THUMB_INTERWORK__ */
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void trap_instruction(void)
 {
 	/* See 'arm-linux-tdep.c' in GDB source.
@@ -81,7 +81,7 @@ __inline__ static void trap_instruction(void)
 }
 #elif defined(__arm__) && !defined(__thumb__)
 	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void trap_instruction(void)
 {
 	/* See 'arm-linux-tdep.c' in GDB source,
@@ -94,7 +94,7 @@ __inline__ static void trap_instruction(void)
 	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_BULTIN_TRAP
 #elif defined(__aarch64__)
 	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void trap_instruction(void)
 {
 	/* See 'aarch64-tdep.c' in GDB source,
@@ -104,7 +104,7 @@ __inline__ static void trap_instruction(void)
 #elif defined(__powerpc__)
 	/* PPC 32 or 64-bit, big or little endian */
 	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void trap_instruction(void)
 {
 	/* See 'rs6000-tdep.c' in GDB source,
@@ -126,20 +126,20 @@ __inline__ static void trap_instruction(void)
 #ifndef DEBUG_BREAK_IMPL
 #error "debugbreak.h is not supported on this target"
 #elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_TRAP_INSTRUCTION
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void debug_break(void)
 {
 	trap_instruction();
 }
 #elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_BULTIN_TRAP
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void debug_break(void)
 {
 	__builtin_trap();
 }
 #elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_SIGTRAP
 #include <signal.h>
-__attribute__((gnu_inline, always_inline))
+__attribute__((always_inline))
 __inline__ static void debug_break(void)
 {
 	raise(SIGTRAP);