Consistent closure compiler args

We we only passing `--max_old_space_size` on non-Windows because
get_npm_cmd has no way to add node arguments (that node command is
embedded within `node_modules/.bin/closure-compiler` so cannot be
modified directly.  Settings NODE_OPTIONS, works on all platforms.

This platform discrepancy dates back to #9989 when
`--max_old_space_size` was first added.

tools/building.py

diff --git a/tools/building.py b/tools/building.py
index 52d523b..b3757ca 100644
--- a/tools/building.py
+++ b/tools/building.py
@@ -512,13 +512,7 @@
     return config.CLOSURE_COMPILER
 
   # Otherwise use the one installed via npm
-  cmd = shared.get_npm_cmd('google-closure-compiler')
-  if not WINDOWS:
-    # Work around an issue that Closure compiler can take up a lot of memory and crash in an error
-    # "FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap
-    # out of memory"
-    cmd.insert(-1, '--max_old_space_size=8192')
-  return cmd
+  return shared.get_npm_cmd('google-closure-compiler')
 
 
 def check_closure_compiler(cmd, args, env, allowed_to_fail):
@@ -543,6 +537,10 @@
 
 def get_closure_compiler_and_env(user_args):
   env = shared.env_with_node_in_path()
+  # Work around an issue that Closure compiler can take up a lot of memory and crash in an error
+  # "FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap
+  # out of memory"
+  env['NODE_OPTIONS'] = '--max_old_space_size=8192'
   closure_cmd = get_closure_compiler()
 
   native_closure_compiler_works = check_closure_compiler(closure_cmd, user_args, env, allowed_to_fail=True)

tools/shared.py

diff --git a/tools/shared.py b/tools/shared.py
index 85d25c8..2d3f90b 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -222,11 +222,8 @@
     cmd = [path_from_root('node_modules/.bin', name + '.cmd')]
   else:
     cmd = [*config.NODE_JS, path_from_root('node_modules/.bin', name)]
-  if not os.path.exists(cmd[-1]):
-    if missing_ok:
-      return None
-    else:
-      exit_with_error(f'{name} was not found! Please run "npm install" in Emscripten root directory to set up npm dependencies')
+  if not missing_ok and os.path.exists(cmd[-1]):
+    exit_with_error(f'{name} was not found! Please run "npm install" in Emscripten root directory to set up npm dependencies')
   return cmd