[build] Don't use bash to run simple commands.

This has some minor advantages, including dune handling of arguments.

dune

@@ -44,7 +44,9 @@
   tsconfig.json
   node_modules)
  (action
-  (bash "npx webpack --config-name cli && chmod +x cli.js")))
+  (progn
+   (run npx webpack --config-name cli)
+   (run chmod +x cli.js))))
 
 ; Just the worker
 (alias

ui-js/dune

@@ -4,8 +4,8 @@
   (source_tree .)
   (source_tree ../coq-jslib)
   ../node_modules)
- (action (bash "npx browserify coq-build.js -d -s coqBuild -o %{targets}"))
-)
+ (action
+  (run npx browserify coq-build.js -d -s coqBuild -o %{targets})))
 
 (rule
  (targets ide-project.browser.js)
@@ -14,4 +14,4 @@
   (source_tree ../coq-jslib/build)
   ../node_modules)
  (action
-  (bash "npx webpack --mode production --config-name ide-project")))
+  (run npx webpack --mode production --config-name ide-project)))