rules.mk: Update ccache's compiler check.

Update the compiler check for ccache so we don't
end up with the wrong binaries. Right now the
compiler check will not be able to correctly
distinguish the compiler used for build
ARMv8 binaries from the one used to build
ARMv7 binaries.

Signed-off-by: Markus Gothe <markus.gothe@genexis.eu>

Link: https://github.com/openwrt/openwrt/pull/16290
Signed-off-by: John Crispin <john@phrozen.org>
(cherry picked from commit 3859e8eeb8)

rules.mk

@@ -344,7 +344,7 @@ ifneq ($(CONFIG_CCACHE),)
   HOSTCXX:= ccache $(HOSTCXX)
   export CCACHE_BASEDIR:=$(TOPDIR)
   export CCACHE_DIR:=$(if $(call qstrip,$(CONFIG_CCACHE_DIR)),$(call qstrip,$(CONFIG_CCACHE_DIR)),$(TOPDIR)/.ccache)
-  export CCACHE_COMPILERCHECK:=%compiler% -dumpmachine; %compiler% -dumpversion
+  export CCACHE_COMPILERCHECK:=%compiler% -v -c
 endif
 
 TARGET_CONFIGURE_OPTS = \