[M] Change in coreboot[main]: lib/string: Add strncat() and strcat() functions

[Julius Werner (Code Review)]

Attention is currently required from: Yu-Ping Wu.

Julius Werner has posted comments on this change by Yu-Ping Wu. ( https://review.coreboot.org/c/coreboot/+/83765?usp=email )

The change is no longer submittable: All-Comments-Resolved is unsatisfied now.

Change subject: lib/string: Add strncat() and strcat() functions
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Patch Set 3:

(2 comments)

Patchset:

PS3: 
This is fine, but if you have extra time I think it would also be a good idea to start merging the standard string functions between coreboot and libpayload in commonlib/bsd.

File src/lib/string.c:

https://review.coreboot.org/c/coreboot/+/83765/comment/ec930fdc_1b34e3c0?usp... :
PS3, Line 107: 	strncpy(dst + strlen(dst), src, count);
This isn't really a great implementation (walks the string twice). Better would be something like:
```
for (size_t i = 0; i < count; i++) {
  dst[i] = src[i];
  if (src[i] == '\0')
    return dst;
}
dst[count - 1)] = '\0';
return dst;
```