Fix typos in hint message (iovisor#2106)

Fix typos in hint message 

Signed-off-by: Paul Chaignon <[email protected]>

src/cc/libbpf.c

@@ -346,9 +346,9 @@ static void bpf_print_hints(int ret, char *log)
 
  // referencing global/static variables or read only data
  if (strstr(log, "unknown opcode") != NULL) {
- fprintf(stderr, "HINT: The 'unknown opcode' can happen if you reference"
- "a global or static variable, or data in read only section. For example,"
- "'char *p = \"hello\"' will result in p referencing a read only section,"
+ fprintf(stderr, "HINT: The 'unknown opcode' can happen if you reference "
+ "a global or static variable, or data in read-only section. For example,"
+ " 'char *p = \"hello\"' will result in p referencing a read-only section,"
  " and 'char p[] = \"hello\"' will have \"hello\" stored on the stack.\n\n");
  }