Fix goma environment on alpine

Author: 1c3t3a

build-bench-env.sh

@@ -512,7 +512,8 @@ if test "$setup_pa" = "1"; then
 
   # Setup depot_tools for building
   git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git --depth=1
-  export PATH="$PATH:$PWD/depot_tools"
+  export PATH="$PWD/depot_tools:$PATH"
+  export GOMA_DIR="$PWD/depot_tools/.cipd_bin"
 
   # Fetch sources - this relies on a standalone build of PA
   gclient config https://github.com/1c3t3a/partition_alloc_builder.git