disable tests for ppc64le, drop logic around QEMU_ARCH

ci/env.sh

@@ -46,8 +46,10 @@ case $TARGET in
         ;;
     powerpc64le-unknown-linux-gnu)
         export PREFIX=powerpc64le-linux-gnu-
-        export QEMU_ARCH=i386
         export QEMU_LD_PREFIX=/usr/powerpc64le-linux-gnu
+        # QEMU crashes, even running the simplest cross compiled C program:
+        # `int main() { return 0; }`
+        export RUN_TESTS=n
         ;;
     thumbv*-none-eabi)
         export CARGO=xargo

ci/install.sh

@@ -3,13 +3,7 @@ set -ex
 . $(dirname $0)/env.sh
 
 install_qemu() {
-    case ${QEMU_ARCH:-$TRAVIS_OS_NAME} in
-        i386)
-            dpkg --add-architecture $QEMU_ARCH
-            apt-get update
-            apt-get install -y --no-install-recommends \
-                    binfmt-support qemu-user-static:$QEMU_ARCH
-            ;;
+    case $TRAVIS_OS_NAME in
         linux)
             apt-get update
             apt-get install -y --no-install-recommends \