Use --fast by default in build_image when --jobs is enabled.

Also update eretry to not pass in $EMERGE_JOBS anymore, in coordination with my previous change, which passed it in directly instead of depending on eretry to do so: http://codereview.chromium.org/2944004/show

TEST=Ran build_image --jobs 2 and build_packages --jobs 2
BUG=none

Review URL: http://codereview.chromium.org/2914004

build_image

@@ -92,6 +92,11 @@ if [ "${FLAGS_rootfs_size}" -gt "${FLAGS_rootfs_partition_size}" ] ; then
   exit 1
 fi
 
+if [ ${FLAGS_jobs} -ne -1 ]; then
+  EMERGE_JOBS="--jobs=${FLAGS_jobs}"
+  FLAGS_fast=${FLAGS_TRUE}
+fi
+
 EMERGE_BOARD_CMD="emerge-${FLAGS_board}"
 if [ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]; then
   echo "Using alternate emerge"
@@ -161,10 +166,6 @@ if [[ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]] ; then
   INSTALL_MASK="${INSTALL_MASK} ${FACTORY_INSTALL_MASK}"
 fi
 
-if [[ ${FLAGS_jobs} -ne -1 ]]; then
-  EMERGE_JOBS="--jobs=${FLAGS_jobs}"
-fi
-
 # Figure out ARCH from the given toolchain.
 # TODO: Move to common.sh as a function after scripts are switched over.
 TC_ARCH=$(echo "${CHOST}" | awk -F'-' '{ print $1 }')

common.sh

@@ -325,14 +325,13 @@ function die {
 }
 
 # Retry an emerge command according to $FLAGS_retries
-# The $EMERGE_JOBS flags will only be added the first time the command is run
 function eretry () {
+  $* && return 0
   local i=
   for i in $(seq $FLAGS_retries); do
     echo Retrying $*
-    $* $EMERGE_JOBS && return 0
+    $* && return 0
   done
-  $* && return 0
   return 1
 }