Make warning for native build

[H. J. Lu]

For a native build, I got

Makefile:6545: warning: overriding commands for target `i686-pc-linux-gnu/libiberty/Makefile'
Makefile:1237: warning: ignoring old commands for target `i686-pc-linux-gnu/libiberty/Makefile'

It is triggered by

configure-build-libiberty: $(BUILD_SUBDIR)/libiberty/Makefile
$(BUILD_SUBDIR)/libiberty/Makefile: config.status
...
configure-target-libiberty: $(TARGET_SUBDIR)/libiberty/Makefile
...
$(TARGET_SUBDIR)/libiberty/Makefile: config.status $(TARGET_SUBDIR)/libiberty/multilib.out

Shouldn't configure comment out the configure-build-libiberty related
targets for native build?


H.J.