[sanitizer] Update x86 ABILIST filtering for x86_64 devices

[rprichard]

Summary

An x86_64 device (e.g. Android emulator or Cuttlefish VM) might have an
ro.product.cpu.abilist like:

x86_64,x86,arm64-v8a,armeabi-v7a,armeabi
x86_64,arm64-v8a,x86,armeabi-v7a,armeabi

When the first arch starts with x86, filter out the remaining archs
that don't start with x86.

[rprichard]

FWIW: The sanitizer tests passed on an x86_64 R emulator (RSR1.200819.001.A1).

[rprichard]

OTOH, my internal master Cuttlefish VM sets ro.product.cpu.abilist to x86_64,arm64-v8a,x86,armeabi-v7a,armeabi.

emulator:

$ adb -s emulator-5554 shell getprop | grep abilist
[ro.product.cpu.abilist]: [x86_64,x86,arm64-v8a,armeabi-v7a,armeabi]
[ro.product.cpu.abilist32]: [x86,armeabi-v7a,armeabi]
[ro.product.cpu.abilist64]: [x86_64,arm64-v8a]

Cuttlefish VM:

$ adb -s 0.0.0.0:6520 shell getprop | grep abilist
[ro.product.cpu.abilist]: [x86_64,arm64-v8a,x86,armeabi-v7a,armeabi]
[ro.product.cpu.abilist32]: [x86,armeabi-v7a,armeabi]
[ro.product.cpu.abilist64]: [x86_64,arm64-v8a]
[ro.system.product.cpu.abilist]: [x86_64,x86,arm64-v8a,armeabi-v7a,armeabi]
[ro.system.product.cpu.abilist32]: [x86,armeabi-v7a,armeabi]
[ro.system.product.cpu.abilist64]: [x86_64,arm64-v8a]
[ro.vendor.product.cpu.abilist]: [x86_64,x86,arm64-v8a,armeabi-v7a,armeabi]
[ro.vendor.product.cpu.abilist32]: [x86,armeabi-v7a,armeabi]
[ro.vendor.product.cpu.abilist64]: [x86_64,arm64-v8a]

[rprichard]

Account for both x86_64,arm64,x86,arm and x86_64,x86,arm64,arm orderings.

zorg/buildbot/builders/sanitizers/buildbot_android_functions.sh

if ! ninja -C llvm_build_android_$_arch llvm-symbolizer ; then
     echo @@@STEP_FAILURE@@@
   fi
   if ! ninja -C compiler_rt_build_android_$_arch ; then
     BUILD_RT_ERR="${BUILD_RT_ERR}|${_arch}|"
     echo @@@STEP_FAILURE@@@
   fi
 }
 
-# If a multiarch device has x86 as the first arch, remove everything else from
-# the list. This captures cases like [x86,armeabi-v7a], where the arm part is
-# software emulation and incompatible with ASan.
+# If a multiarch device's first arch starts with x86, remove archs that don't
+# start with x86. Handle cases like:
+#  - x86,armeabi-v7a
+#  - x86_64,x86,arm64-v8a,armeabi-v7a,armeabi
+#  - x86_64,arm64-v8a,x86,armeabi-v7a,armeabi
+# The arm part is software emulation and incompatible with ASan.
 function patch_abilist { # IN OUT
   local _abilist=$1
   local _out=$2
-  if [[ "$_abilist" == "x86,"* ]]; then
-    _abilist="x86"
+  if [[ "$_abilist" == "x86"* ]]; then
+    _abilist=$(echo $_abilist | tr , '\n' | grep '^x86')
+    _abilist=$(echo $_abilist | tr ' ' ,)
   fi
   eval $_out="'$_abilist'"
 }
 
 function restart_adb_server {
   ADB=adb
   echo @@@BUILD_STEP restart adb server@@@
   $ADB kill-server
   sleep 2
   $ADB start-server
   sleep 2
 }
 
 function test_on_device {
   local _serial=$1
   shift
 
   ABILIST=$(${ADB} -s $_serial shell getprop ro.product.cpu.abilist)
-  patch_abilist $ABILIST ABILIST
+  patch_abilist "$ABILIST" ABILIST
   for _arg in "$@"; do
     local _arch=${_arg%:*}
     local _abi=${_arg#*:}
     if [[ $BUILD_RT_ERR == *"|${_arch}|"* ]]; then
       echo "@@@STEP_FAILURE@@ skipping tests on ${_arch}"
       continue
     fi
     if [[ $ABILIST == *"$_abi"* ]]; then