compile-rt: Fix building compiler-native on aarch64 build hosts.

compile-rt: Fix building compiler-native on aarch64 build hosts.

Using target triple confuses the native system compiler to find
libgcc and C runtime during compiler-rt-native build

Fixes
|     /home/khem/yoe/build/tmp/hosttools/ld: cannot find crtbeginS.o: No such file or directory
|     /home/khem/yoe/build/tmp/hosttools/ld: cannot find -lgcc: No such file or directory
|     /home/khem/yoe/build/tmp/hosttools/ld: cannot find -lgcc_s: No such file or directory
|     clang: error: linker command failed with exit code 1 (use -v to see invocation)
|     ninja: build stopped: subcommand failed.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>