clang/musl progress and a small bug.

[Richard Pennington <rich@pennware.com>]

Hi,

clang's libcompiler-rt doesn't have support for crtbegin.o and crtend.o so 
global constructors and destructors didn't work out of the box. If I link with 
the NetBSD versions of crtbegin.c and crtend.c in place of the musl crti.s and 
crtn.s everything works fine. For now, I've added them to the musl build under 
crt.

I think I found a bug while running my library regression test. The zero test 
failed in the following code:

    TEST_TRACE(C99 7.20.3.1)
    p = calloc(100, sizeof(char));
    TEST(p != NULL, "calloc() returned a pointer");
    int flag = 1;
    for (i = 0; i < 100; ++i) {
        if (p[i] != 0) {
            flag = 0;
        }
    }
    TEST(flag, "calloc() returned zeroed memory");

The TEST() macro is kind of like assert but it prints out the message and 
counts failures and successes:

PASS: 001stdlib.c:74: Stdlib(Stdlib): calloc() returned a pointer
FAIL: 001stdlib.c:81: Stdlib(Stdlib): calloc() returned zeroed memory
Stdlib unit tests completed
    32 tests run
    1 test failed

Am I missing something?

-Rich