Hide __cpu_indicator_init/__cpu_model from linker

Hide __cpu_indicator_init/__cpu_model from linker

We shouldn't call external function, __cpu_indicator_init, while an object
is being relocated since its .got.plt section hasn't been updated.  It
works for non-PIE since no update on .got.plt section is required.  This
patch creates libgcc.so as a linker script, hides __cpu_indicator_init
and __cpu_model in libgcc.so.1 from linker, forces linker to resolve
__cpu_indicator_init and __cpu_model to their hidden definitions in
libgcc.a while providing backward binary compatibility.

gcc/testsuite/

	PR target/65612
	* g++.dg/ext/mv18.C: New test.
	* g++.dg/ext/mv19.C: Likewise.
	* g++.dg/ext/mv20.C: Likewise.
	* g++.dg/ext/mv21.C: Likewise.
	* g++.dg/ext/mv22.C: Likewise.
	* g++.dg/ext/mv23.C: Likewise.

libgcc/

	PR target/65612
	* config.host (tmake_file): Add t-slibgcc-libgcc for Linux/x86.
	* config/i386/cpuinfo.c (__cpu_model): Initialize.
	(__cpu_indicator_init@GCC_4.8.0): New.
	(__cpu_model@GCC_4.8.0): Likewise.
	* config/i386/t-linux (HOST_LIBGCC2_CFLAGS): Add
	-DUSE_ELF_SYMVER.

From-SVN: r222178