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. ' -c' is added to make the Broadcom toolchains happy.
Change-Id: I6755d4bc040262396bdd407f67840900a81889e2
Edited by Markus Gothe