tools: xz: force building without ccache

Since XZ is required to bootstrap ccache we must not use the ccache compiler
wrapper to avoid circular dependencies.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

tools/xz/Makefile

@@ -18,6 +18,9 @@ HOST_BUILD_PARALLEL:=1
 
 include $(INCLUDE_DIR)/host-build.mk
 
+HOSTCC := $(HOSTCC_NOCACHE)
+HOSTCXX := $(HOSTCXX_NOCACHE)
+
 HOST_CONFIGURE_ARGS += \
 	--enable-static=yes \
 	--enable-shared=no \