Avoid Expect clobbering stdout when stdin isn't a tty.

Doing expect_after before a child process has been spawned causes Expect
to try reading from stdin. If stdin is /dev/null, it gets an EOF from
the read, assumes it's been closed... and closes stdout too, so we don't
see any more of the child process interaction.

build/build.tcl

@@ -115,7 +115,11 @@ proc build_macsyma_portion {} {
 }
 
 set timeout 100
-expect_after timeout abort
+proc setup_timeout {} {
+    # Don't do this until after you've called "spawn", otherwise it'll cause a
+    # read from stdin which will return EOF if stdin isn't a tty.
+    expect_after timeout abort
+}
 
 set ip [ip_address [lindex $argv 0]]
 set gw [ip_address [lindex $argv 1]]

build/klh10/build.tcl

@@ -7,6 +7,7 @@ set emulator_escape "\034"
 
 proc start_salv {} {
     uplevel #0 {spawn ./kn10-ks-its nsalv.ini}
+    setup_timeout
     expect "EOF"
     respond "KLH10#" "go\r"
 }
@@ -20,12 +21,14 @@ proc start_dskdmp {} {
     #respond "KLH10>" "zero\r"
     quit_emulator
     uplevel #0 {spawn ./kn10-ks-its dskdmp.ini}
+    setup_timeout
     expect "EOF"
     respond "KLH10#" "go\r"
 }
 
 proc start_its {} {
     uplevel #0 {spawn ./kn10-ks-its dskdmp.ini}
+    setup_timeout
     expect "EOF"
     respond "KLH10#" "go\r"
 }

build/simh/build.tcl

@@ -4,6 +4,8 @@ set emulator_escape "\034"
 
 proc start_salv {} {
     uplevel #0 {spawn pdp10 build/simh/init}
+    setup_timeout
+
     respond "sim>" "show ver\r"
     respond "sim>" "b tu1\r"
     expect "MTBOOT"
@@ -23,6 +25,7 @@ proc start_dskdmp {} {
 
 proc start_its {} {
     uplevel #0 {spawn pdp10 build/simh/boot}
+    setup_timeout
 }
 
 proc mount_tape {file} {

build/sims/build.tcl

@@ -4,6 +4,7 @@ set emulator_escape "\034"
 
 proc start_salv {} {
     uplevel #0 {spawn ./tools/sims/BIN/ka10 build/sims/init}
+    setup_timeout
     expect "MAGDMP\r\n"; send "l\033ddt\r"
     expect "\n"; send "t\033salv\r"
 }
@@ -19,6 +20,7 @@ proc start_dskdmp args {
     }
     set foo "spawn ./tools/sims/BIN/ka10 $ini"
     uplevel #0 $foo
+    setup_timeout
 }
 
 proc mount_tape {file} {