[clang] Remove setjmp that is causing problems in the models in linux.

Summary:
@public
Remove setjmp that is causing problems in the models in linux.
Will investigate and add it again later.

Test Plan: All the models are now created. In particular strcpy, strdup and a few others in the beginning of the file.

infer/models/c/src/libc_basic.c

@@ -212,7 +212,6 @@ void rewind(FILE *stream);
 int scanf(const char *format, ...); // builtin: modeled internally
 void setbuf(FILE * __restrict stream, char * __restrict buf);
 int setitimer(int which, const struct itimerval *__restrict value, struct itimerval *__restrict ovalue);
-int setjmp(jmp_buf env);
 char *setlocale(int category, const char *locale);
 int setlogin(const char *name);
 int setpassent(int stayopen);
@@ -781,11 +780,6 @@ void rewind(FILE *stream) {
     tmp = *stream;
 }
 
-// modeled as just return a nondeterministic value
-int setjmp(jmp_buf env) {
-  return __infer_nondet_int();
-}
-
 // modeled as exit()
 void longjmp(jmp_buf env, int val) {
   exit(0);