hostid: improve extremely unreadable parts

*: remove checks of sigaction and sigprocmask results
 in cases where they clearly can't fail:
 sigaction(known_good_sig)
 sigprocmask(known_good_how)

    text           data     bss     dec     hex filename
-    393              4       0     397     18d libc/pwd_grp/lckpwdf.o
+    382              4       0     386     182 libc/pwd_grp/lckpwdf.o
-     56              0       0      56      38 libc/signal/sigblock.o
+     44              0       0      44      2c libc/signal/sigblock.o
-    211              0       0     211      d3 libc/signal/sigset.o
+    202              0       0     202      ca libc/signal/sigset.o
-     56              0       0      56      38 libc/signal/sigsetmask.o
+     44              0       0      44      2c libc/signal/sigsetmask.o
-    309              0       0     309     135 libc/unistd/sleep.o
+    256              0       0     256     100 libc/unistd/sleep.o

1 files changed, 1 insertions, 0 deletions

diff --git a/libc/signal/sigintr.c b/libc/signal/sigintr.c
index 23f87e199..1a8d60eb2 100644
--- a/libc/signal/sigintr.c
+++ b/libc/signal/sigintr.c
@@ -34,6 +34,7 @@ int siginterrupt (int sig, int interrupt)
 #ifdef	SA_RESTART
   struct sigaction action;
 
+  /* Fails if sig is bad.  */
   if (sigaction (sig, NULL, &action) < 0)
     return -1;