Fix 'emsdk install sdk-main-64bit' to produce a functioning installation. (#1444)

Author: juj

emsdk.py

@@ -1332,6 +1332,17 @@ def emscripten_npm_install(tool, directory):
       return False
 
   print('Done running: npm ci')
+
+  if os.path.isfile(os.path.join(directory, 'bootstrap.py')):
+    try:
+      subprocess.check_output([sys.executable, os.path.join(directory, 'bootstrap.py')],
+                              cwd=directory, stderr=subprocess.STDOUT, env=env,
+                              universal_newlines=True)
+    except subprocess.CalledProcessError as e:
+      errlog('Error running %s:\n%s' % (e.cmd, e.output))
+      return False
+
+    print('Done running: Emscripten bootstrap')
   return True