Auto merge of #45810 - SimonSapin:ac-dc, r=aturon

Disable LLVM assertions on Nightly, enable them in "alt" builds.

Per IRC discussion https://mozilla.logbot.info/rust-infra/20171106#c13812170-c13812204

Background: https://internals.rust-lang.org/t/disabling-llvm-assertions-in-nightly-builds/5388/14

.travis.yml

@@ -16,14 +16,14 @@ matrix:
       if: type = pull_request OR branch = auto
 
     - env: IMAGE=dist-x86_64-linux DEPLOY=1
-      if: branch = try OR branch = auto
+      if: branch = auto
 
     # "alternate" deployments, these are "nightlies" but don't have assertions
     # turned on, they're deployed to a different location primarily for projects
     # which are stuck on nightly and don't want llvm assertions in the artifacts
     # that they use.
     - env: IMAGE=dist-x86_64-linux DEPLOY_ALT=1
-      if: branch = auto
+      if: branch = try OR branch = auto
 
     - env: >
         RUST_CHECK_TARGET=dist
@@ -322,7 +322,7 @@ deploy:
       secure: "kUGd3t7JcVWFESgIlzvsM8viZgCA9Encs3creW0xLJaLSeI1iVjlJK4h/2/nO6y224AFrh/GUfsNr4/4AlxPuYb8OU5oC5Lv+Ff2JiRDYtuNpyQSKAQp+bRYytWMtrmhja91h118Mbm90cUfcLPwkdiINgJNTXhPKg5Cqu3VYn0="
     on:
       branch: try
-      condition: $DEPLOY = 1
+      condition: $DEPLOY_ALT = 1
 
   # this is the same as the above deployment provider except that it uploads to
   # a slightly different directory and has a different trigger

src/bootstrap/config.rs

@@ -528,7 +528,7 @@ impl Config {
         // Now that we've reached the end of our configuration, infer the
         // default values for all options that we haven't otherwise stored yet.
 
-        let default = config.channel == "nightly";
+        let default = false;
         config.llvm_assertions = llvm_assertions.unwrap_or(default);
 
         let default = match &config.channel[..] {

src/ci/run.sh

@@ -49,7 +49,7 @@ if [ "$DEPLOY$DEPLOY_ALT" != "" ]; then
   if [ "$NO_LLVM_ASSERTIONS" = "1" ]; then
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-llvm-assertions"
   elif [ "$DEPLOY_ALT" != "" ]; then
-    RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-llvm-assertions"
+    RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-llvm-assertions"
   fi
 else
   # We almost always want debug assertions enabled, but sometimes this takes too