kbuild: dummy-tools: pretend we understand -fpatchable-function-entry

Commit 0f71dcf ("powerpc/ftrace: Add support for
-fpatchable-function-entry") added a script to check for
-fpatchable-function-entry compiler support. The script expects compiler
to emit the section __patchable_function_entries and few nops after a
function entry.

If the compiler understands and emits the above,
CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY is set.

So teach dummy-tools' gcc about this.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Author: Jiri Slaby (SUSE)

scripts/dummy-tools/gcc

@@ -91,6 +91,16 @@ if arg_contain -S "$@"; then
 		fi
 		exit 0
 	fi
+
+	# For arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
+	if arg_contain -m64 "$@" && arg_contain -fpatchable-function-entry=2 "$@"; then
+		echo "func:"
+		echo ".section __patchable_function_entries"
+		echo ".localentry"
+		echo "  nop"
+		echo "  nop"
+		exit 0
+	fi
 fi
 
 # To set GCC_PLUGINS