[bazel] Allow ./bazelisk.sh to use --bazelrc flags

These flags need to come _before_ the subcommand, i.e.:

```
bazel --bazelrc=... cquery # VALID
bazel cquery --bazelrc=... # INVALID
```

which is done in this script by pushing flags that come before the
subcommand name into an array and re-applying them in the correct order
later.

If these Bash arrays are confusing and you've come across this commit in
a `git blame` then hopefully this will help:

1. Bash supports arrays defined using parentheses: `array=("foo" "bar")`
2. Arrays can't be passed as arguments to functions, they are expanded
   and get mixed into other arguments.
3. Names of arrays _can_ be passed as arguments, and Bash lets us
   re-create a variable pointing at an array using its name: `${!name}`.
4. the syntax for expanding an array into its elements with correct
   quoting on each is: `"${array[@]}"`.

Signed-off-by: James Wainwright <[email protected]>

bazelisk.sh

@@ -93,10 +93,18 @@ function outquery_starlark_expr() {
     esac
 }
 
+# Arguments:
+# $qexpr: starlark expression - see `outquery_starlark_expr`
+# $name: name of an array containing Bazel arguments that should come _before_
+#        the subcommand (e.g. `--bazelrc=...`).
 function do_outquery() {
-    local qexpr="$1"
-    shift
-    "$file" cquery "$@" \
+    local qexpr="$1"; shift
+    # Bash can't pass whole arrays through functions so we pass the name of the
+    # array instead and expand it.
+    local name="$1"; shift
+    local pre_cmd_args=("${!name}")
+
+    "$file" "${pre_cmd_args[@]}" cquery "$@" \
         --output=starlark --starlark:expr="$qexpr" \
         --ui_event_filters=-info --noshow_progress
 }
@@ -121,6 +129,14 @@ function main() {
         fi
     fi
 
+    # Shift all flags (starting with `-`) that come before the subcommand
+    # into an array.
+    pre_cmd_args=()
+    while [[ "$1" == -* ]]; do
+        pre_cmd_args+=("$1")
+        shift
+    done
+
     case "${1-}" in
         outquery*)
             # The custom 'outquery' command can be used to query bazel for the
@@ -130,10 +146,9 @@ function main() {
             #   outquery-all: return all output files associated with the label.
             #   outquery-x: return output files containing the substring "x".
             #   outquery.x: return output files ending with the substring ".x".
-            local qexpr
-            qexpr="$(outquery_starlark_expr "$1")"
+            local qexpr="$(outquery_starlark_expr "$1")"
             shift
-            do_outquery "$qexpr" "$@"
+            do_outquery "$qexpr" pre_cmd_args "$@"
             ;;
         build-then)
             # The 'build-then' command builds the requested targets and then
@@ -149,14 +164,14 @@ function main() {
             shift
             local qexpr outfile
             qexpr="$(outquery_starlark_expr outquery)"
-            outfile=$(do_outquery "$qexpr" "$@")
-            "$file" build "$@"
+            outfile=$(do_outquery "$qexpr" pre_cmd_args "$@")
+            "$file" "${pre_cmd_args[@]}" build "$@"
             # shellcheck disable=SC2059
             # We are intentionally using $command_template as a format string.
             eval "$(printf "$command_template" "$outfile")"
             ;;
         *)
-            exec "$file" "$@"
+            exec "$file" "${pre_cmd_args[@]}" "$@"
             ;;
     esac
 }