add Print:flush()

Author: hathach

.github/workflows/githubci.yml

@@ -24,11 +24,6 @@ jobs:
         - 'ledglasses_nrf52840'
 
     steps:
-    - name: Setup Python
-      uses: actions/setup-python@v4
-      with:
-        python-version: '3.x'
-        
     - name: Checkout code
       uses: actions/checkout@v4
       with:

cores/nRF5/Print.h

@@ -98,6 +98,8 @@ class Print
     {
       return printBufferReverse((uint8_t const*) buffer, size, delim, byteline);
     }
+
+    virtual void flush() { /* Empty implementation for backward compatibility */ }
 };
 
 #endif