kconfig: shorten the temporary directory name for cc-option

The cc-option macro creates the temporary directory, .tmp_$$$$.
Shell expands '$$' into its process ID. '$$$$' results in repeated PID.

In Makefile, '$$$$' is correct (see TMPOUT in scripts/Malefile.compiler)
because '$$' is an escape sequence of '$'. Make expands '$$$$' into '$$',
then shell expands it into the process ID.

This does not apply to Kconfig because Kconfig requires variable
references to be enclosed by curly braces, like ${variable}.
The '$' that is not followed by '{' loses its effect.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>

scripts/Kconfig.include

@@ -25,7 +25,7 @@ failure = $(if-success,$(1),n,y)
 
 # $(cc-option,<flag>)
 # Return y if the compiler supports <flag>, n otherwise
-cc-option = $(success,mkdir .tmp_$$$$; trap "rm -rf .tmp_$$$$" EXIT; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$$$/tmp.o)
+cc-option = $(success,mkdir .tmp_$$; trap "rm -rf .tmp_$$" EXIT; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$/tmp.o)
 
 # $(ld-option,<flag>)
 # Return y if the linker supports <flag>, n otherwise