Build fails on Buildroot due to unsupported target_clones

[Carlos Santos]

Porting stress-ng to Buildroot + uClibc-ng I stomped on several compilation errors like this:

stress-cpu.c:2041:27: error: the call requires ifunc, which is not supported by this target
 static void TARGET_CLONES stress_cpu_union(const char *name)
                           ^~~~~~~~~~~~~~~~

I solved the problem by means of a test program which checks if the target_clones attribute can be used with the current toolchain (see attached patch).

[Colin Ian King (colin-king)]

Thanks Carlos, fix committed and pushed (with some minor adjustments)