Fix PATH setup for arm64.

On architectures other than "arm", the combination of
ANDROID_KERNEL_TOOLCHAIN_PATH being empty, and CODE_REVIEWS being empty,
leads to adding a :: into the user's PATH, which is highly undesirable.

Neither CODE_REVIEWS nor the mips toolchaindir is ever used, so just
remove them, and make sure we only include the extra colon when setting
the kernel toolchain path to a non-empty value.

Change-Id: I2dfa7d3a322b56b6abbc47476082dc6ae4dd6a82
diff --git a/envsetup.sh b/envsetup.sh
index 3b9423b..f75bf88 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -115,7 +115,6 @@
     fi
 
     # and in with the new
-    CODE_REVIEWS=
     prebuiltdir=$(getprebuilt)
     gccprebuiltdir=$(get_abs_build_var ANDROID_GCC_PREBUILTS)
 
@@ -160,12 +159,10 @@
             # Legacy toolchain configuration used for ARM kernel compilation
             toolchaindir=arm/arm-eabi-$targetgccversion/bin
             if [ -d "$gccprebuiltdir/$toolchaindir" ]; then
-                 ANDROID_KERNEL_TOOLCHAIN_PATH="$gccprebuiltdir/$toolchaindir"
-                 export ARM_EABI_TOOLCHAIN=$ANDROID_KERNEL_TOOLCHAIN_PATH
+                 export ARM_EABI_TOOLCHAIN="$gccprebuiltdir/$toolchaindir"
+                 ANDROID_KERNEL_TOOLCHAIN_PATH="$ARM_EABI_TOOLCHAIN":
             fi
             ;;
-        mips) toolchaindir=mips/mips-eabi-4.4.3/bin
-            ;;
         *)
             # No need to set ARM_EABI_TOOLCHAIN for other ARCHs
             ;;
@@ -173,7 +170,7 @@
 
     export ANDROID_QTOOLS=$T/development/emulator/qtools
     export ANDROID_DEV_SCRIPTS=$T/development/scripts:$T/prebuilts/devtools/tools
-    export ANDROID_BUILD_PATHS=$(get_build_var ANDROID_BUILD_PATHS):$ANDROID_QTOOLS:$ANDROID_TOOLCHAIN:$ANDROID_KERNEL_TOOLCHAIN_PATH$CODE_REVIEWS:$ANDROID_DEV_SCRIPTS:
+    export ANDROID_BUILD_PATHS=$(get_build_var ANDROID_BUILD_PATHS):$ANDROID_QTOOLS:$ANDROID_TOOLCHAIN:$ANDROID_KERNEL_TOOLCHAIN_PATH$ANDROID_DEV_SCRIPTS:
     export PATH=$ANDROID_BUILD_PATHS$PATH
 
     unset ANDROID_JAVA_TOOLCHAIN