Hello.

This fixes ICE when one does not provide valid target names:
__attribute__((target_clones("default,foo,bar")))

In that situation I suggest to print:

$ ./xgcc -B. /tmp/mvc-ice.c
/tmp/mvc-ice.c:6:1: error: attribute(target("foo")) is unknown
 foo ()
 ^~~
/tmp/mvc-ice.c:6:1: error: attribute(target("bar")) is unknown
/tmp/mvc-ice.c: In function ‘foo.resolver’:
cc1: fatal error: At least one more version other than the default is expected

Should I add a test-case for a fatal error?

Thanks,
Martin