Merge #269

269: [v0.4.x] CI: pin to an older nightly r=korken89 a=japaric

to workaround compiletest-rs being broken on recent nightlies

this is a backport of #267 and it's required to land #265 

I'm not backporting #268  (compiletest -> trybuild) because this branch has compile-pass tests which depend on compiletest and can't be ported to trybuild

Co-authored-by: Jorge Aparicio <jorge@japaric.io>

ci/install.sh

@@ -1,10 +1,13 @@
 set -euxo pipefail
 
 main() {
-    if [ $TARGET != x86_64-unknown-linux-gnu ]; then
-        rustup target add $TARGET
+    if [ $TARGET = x86_64-unknown-linux-gnu ]; then
+        # needed by compiletest-rs
+        rustup component add rustc-dev
     fi
 
+    rustup target add $TARGET
+
     mkdir qemu
     curl -L https://github.com/japaric/qemu-bin/raw/master/14.04/qemu-system-arm-2.12.0 > qemu/qemu-system-arm
     chmod +x qemu/qemu-system-arm