Remove unused mkstemp()

b82c231 "Remove -i option (#704)" removed its last usage in 2015.

Spotted while looking for code could potentially write/create/modify files.

src/util.c

@@ -79,27 +79,6 @@ FILE *fopen(const char *fname, const char *mode) {
 }
 #endif
 
-#ifndef HAVE_MKSTEMP
-int mkstemp(char *template) {
-  size_t len = strlen(template);
-  int tries=5;
-  int fd;
-
-  // mktemp() truncates template when it fails
-  char *s = alloca(len + 1);
-  assert(s != NULL);
-  strcpy(s, template);
-
-  do {
-    // Restore template
-    strcpy(template, s);
-    (void) mktemp(template);
-    fd = open(template, O_CREAT | O_EXCL | O_RDWR, 0600);
-  } while (fd == -1 && tries-- > 0);
-  return fd;
-}
-#endif
-
 jv expand_path(jv path) {
   assert(jv_get_kind(path) == JV_KIND_STRING);
   const char *pstr = jv_string_value(path);

src/util.h

@@ -13,10 +13,6 @@
 
 #include "jv.h"
 
-#ifndef HAVE_MKSTEMP
-int mkstemp(char *template);
-#endif
-
 jv expand_path(jv);
 jv get_home(void);
 jv jq_realpath(jv);