Revert "Remove legacy kernel build toolchain PATH setup in envsetup.sh"

This reverts commit 750396d.

envsetup.sh

@@ -221,8 +221,23 @@ function setpaths()
         export ANDROID_TOOLCHAIN_2ND_ARCH=$gccprebuiltdir/$toolchaindir2
     fi
 
+    unset ANDROID_KERNEL_TOOLCHAIN_PATH
+    case $ARCH in
+        arm)
+            # Legacy toolchain configuration used for ARM kernel compilation
+            toolchaindir=arm/arm-eabi-$targetgccversion/bin
+            if [ -d "$gccprebuiltdir/$toolchaindir" ]; then
+                 export ARM_EABI_TOOLCHAIN="$gccprebuiltdir/$toolchaindir"
+                 ANDROID_KERNEL_TOOLCHAIN_PATH="$ARM_EABI_TOOLCHAIN":
+            fi
+            ;;
+        *)
+            # No need to set ARM_EABI_TOOLCHAIN for other ARCHs
+            ;;
+    esac
+
     export ANDROID_DEV_SCRIPTS=$T/development/scripts:$T/prebuilts/devtools/tools:$T/external/selinux/prebuilts/bin
-    export ANDROID_BUILD_PATHS=$(get_build_var ANDROID_BUILD_PATHS):$ANDROID_TOOLCHAIN:$ANDROID_TOOLCHAIN_2ND_ARCH:$ANDROID_DEV_SCRIPTS:
+    export ANDROID_BUILD_PATHS=$(get_build_var ANDROID_BUILD_PATHS):$ANDROID_TOOLCHAIN:$ANDROID_TOOLCHAIN_2ND_ARCH:$ANDROID_KERNEL_TOOLCHAIN_PATH$ANDROID_DEV_SCRIPTS:
 
     # If prebuilts/android-emulator/<system>/ exists, prepend it to our PATH
     # to ensure that the corresponding 'emulator' binaries are used.