[sanitizer_common][test] Fix huge_malloc.c UNSUPPORTED syntax

`lit` doesn't accept arbitrary substrings of the target triple any longer,
so d5a779b
<https://reviews.llvm.org/rGd5a779b5a39b655ed9fafedaacbb017c46f5dbfe> has
no effect.

Instead, this patch uses the `target=` syntax as all other tests in
`compiler-rt`.

Tested on `amd64-pc-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D154298

Author: rorth

compiler-rt/test/sanitizer_common/TestCases/Posix/huge_malloc.c

@@ -13,7 +13,7 @@
 // UNSUPPORTED: hwasan
 
 // FIXME: Something wrong with MADV_FREE or MAP_NORESERVE there.
-// UNSUPPORTED: solaris
+// UNSUPPORTED: target={{.*solaris.*}}
 
 void *p;