fall back to old behavior when deciding mem availablity during build

hack/lib/golang.sh

@@ -421,12 +421,18 @@ kube::golang::build_binaries_for_platform() {
 kube::golang::get_physmem() {
   local mem
 
-  # Linux, in kb
+  # Linux kernel version >=3.14, in kb
   if mem=$(grep MemAvailable /proc/meminfo | awk '{ print $2 }'); then
     echo $(( ${mem} / 1048576 ))
     return
   fi
 
+  # Linux, in kb
+  if mem=$(grep MemTotal /proc/meminfo | awk '{ print $2 }'); then
+    echo $(( ${mem} / 1048576 ))
+    return
+  fi
+
   # OS X, in bytes. Note that get_physmem, as used, should only ever
   # run in a Linux container (because it's only used in the multiple
   # platform case, which is a Dockerized build), but this is provided