Allow trigger build ci to build with specified c++ standard manually

Author: halx99

.github/workflows/build.yml

@@ -15,6 +15,18 @@ on:
       - '**.md'
       - '**/*.md.in'
       - 'docs/**'
+  workflow_dispatch:
+    inputs:
+      cxxstd:
+        # actions run ID
+        description: 'Please input cxxstd, example: 23'
+        # Default value if no value is explicitly provided
+        default: '23'
+        # Input has to be provided for the workflow to run
+        required: false
+
+env:
+  __1K_CXXSTD: '${{ inputs.cxxstd }}'
 
 jobs:
   win32: