Add awk as a default tool for Bazel shell commands.

Apparently
https://github.com/gflags/gflags/blob/e292e0452fcfd5a8ae055b59052fc041cbab4abf/bazel/gflags.bzl#L8
assumes it should be accessible. Normally we could ask them to fix, but
I would expect awk to be a commonly assumed.

The rough search
https://github.com/search?q=filename%3ABUILD+genrule+awk&type=Code
brings ~1K hits.

pkgs/development/tools/build-managers/bazel/default.nix

@@ -1,6 +1,6 @@
 { stdenv, callPackage, lib, fetchurl, fetchpatch, runCommand, makeWrapper
 , jdk, zip, unzip, bash, writeCBin, coreutils
-, which, python, perl, gnused, gnugrep, findutils
+, which, python, perl, gawk, gnused, gnugrep, findutils
 # Apple dependencies
 , cctools, clang, libcxx, CoreFoundation, CoreServices, Foundation
 # Allow to independently override the jdks used to build and run respectively
@@ -23,7 +23,7 @@ let
     for i in ${builtins.toString srcDeps}; do cp $i $out/$(stripHash $i); done
   '';
 
-  defaultShellPath = lib.makeBinPath [ bash coreutils findutils gnugrep gnused which unzip ];
+  defaultShellPath = lib.makeBinPath [ bash coreutils findutils gawk gnugrep gnused which unzip ];
 
 in
 stdenv.mkDerivation rec {