Minor cleanup to the bindgen scripts

components/style/binding_tools/regen.sh

@@ -8,13 +8,15 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
+TOOLS_DIR="$(dirname ${0})"
+
 if [[ ${#} -eq 0 ]]; then
   echo "Usage: ${0} /path/to/gecko/objdir [other-regen.py-flags]"
   exit 1
 fi
 
 # Check for rust-bindgen
-if [[ ! -d rust-bindgen ]]; then
+if [[ ! -d "${TOOLS_DIR}/rust-bindgen" ]]; then
   echo "rust-bindgen not found. Run setup_bindgen.sh first."
   exit 1
 fi
@@ -22,7 +24,7 @@ fi
 # Check for /usr/include
 if [[ ! -d /usr/include ]]; then
   echo "/usr/include doesn't exist." \
-       "Mac users may need to run xcode-select --install."
+       "Mac users may need to run 'xcode-select --install.'"
   exit 1
 fi
 
@@ -32,4 +34,4 @@ else
   LIBCLANG_PATH="$(brew --prefix llvm38)/lib/llvm-3.8/lib"
 fi
 
-./regen.py --target all "${@}"
+"./${TOOLS_DIR}/regen.py" --target all "${@}"