Refactor how CCache is set up

* Use RULE_LAUNCH_COMPILE property as you're apparently supposed to
* Detect if compiler is already ccache to prevent build failure

cmake/SetupCCache.cmake

@@ -0,0 +1,19 @@
+include(FindPackageMessage)
+
+find_program(CCACHE "ccache")
+
+cmake_dependent_option(USE_CCACHE "Use CCache to speed up repeated builds." ON CCACHE OFF)
+
+if (NOT CCACHE OR NOT USE_CCACHE)
+    return()
+endif()
+
+# Fedora, and probably also Red Hat-based distros in general, use CCache by default if it's installed on the system.
+# We'll try to detect this here, and exit if that's the case.
+# Trying to launch ccache with ccache as we'd otherwise do seems to cause build issues.
+if (CMAKE_C_COMPILER MATCHES "ccache" OR CMAKE_CXX_COMPILER MATCHES "ccache")
+    return()
+endif()
+
+find_package_message(CCache "Using CCache to speed up compilation" "${USE_CCACHE}")
+set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE}")