Fix CI for demoted targets

i686-apple-darwin and other 32bit Apple targets ware demoted to tier-3 due
to lack of support from the vendor, and is no longer available from rustup
for nightly, shortly beta.

DockerOSX32 job was removed as it only tests on nightly. BuildChannelsOSX job
will continue testing on these targets on older compilers (stable and below).

ci/azure.yml

@@ -99,18 +99,6 @@ jobs:
         x86_64-apple-darwin:
           TARGET: x86_64-apple-darwin
 
-  - job: DockerOSX32
-    pool:
-      vmImage: macos-10.13
-    steps:
-      - template: azure-install-rust.yml
-      - bash: LIBC_CI=1 sh ./ci/run.sh $TARGET
-        displayName: Execute run.sh
-    strategy:
-      matrix:
-        i686-apple-darwin:
-          TARGET: i686-apple-darwin
-
   - job: Windows
     pool:
       vmImage: vs2017-win2016

ci/build.sh

@@ -147,12 +147,15 @@ x86_64-unknown-linux-gnux32 \
 
 RUST_OSX_TARGETS="\
 aarch64-apple-ios \
+x86_64-apple-darwin \
+x86_64-apple-ios \
+"
+
+RUST_LT_1_42_OSX_TARGETS="\
 armv7-apple-ios \
 armv7s-apple-ios \
 i386-apple-ios \
 i686-apple-darwin \
-x86_64-apple-darwin \
-x86_64-apple-ios \
 "
 
 # The targets are listed here alphabetically
@@ -178,6 +181,12 @@ case "${OS}" in
         ;;
     osx*)
         TARGETS="${RUST_OSX_TARGETS}"
+
+        if [ "${RUST}" != "nightly" ]; then
+            if [ "${RUST}" != "beta" ]; then
+                TARGETS="${TARGETS} ${RUST_LT_1_42_OSX_TARGETS}"
+            fi
+        fi
         ;;
     *)
         ;;