[PR target/65181] nvptx libgcc: Prevent building "advanced" stuff (for example, gcov...

[PR target/65181] nvptx libgcc: Prevent building "advanced" stuff (for example, gcov support)

When building GCC against a proper newlib sysroot, the libgcc build will
include more than what's built in the -Dinhibit_libc configuration used when
building newlib as part of the GCC build process.  See the inhibit_libc logic
in gcc/configure.ac.

To avoid...

    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Type or alignment of argument does not match formal parameter 'ptr'
    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Call has wrong number of parameters
    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Type or alignment of argument does not match formal parameter 'size'
    ptxas fatal   : Ptx assembly aborted due to errors
    nvptx-as: ptxas returned 255 exit status
    make[2]: *** [_gcov_indirect_call_topn_profiler.o] Error 1

..., "dumb down" the libgcc build:

	libgcc/
	PR target/65181
	* config/nvptx/t-nvptx (INHIBIT_LIBC_CFLAGS): Define to
	-Dinhibit_libc.

From-SVN: r220915