Arch Linux

LLVM's code generation backend uses the runtime library to lower instructions that are not supported natively by the architecture. Many of the symbols are also exposed by the GNU runtime library so this is generally a non-issue, but there are missing symbols the backend expects to find.

A simple sample program, as an example:

```
#include <stdio.h>
#include <inttypes.h>

int main(void) {
int64_t x = 5;
int64_t y = 10;
int64_t result = x * y;
printf("%" PRId64 "\n", result);
return 0;
}
```

If you build with checked overflow support (-ftrapv) on i686, the `__mulodi4` symbol will fail to be found because it's supported by compiler-rt but not libgcc_s.