Add minimum permissions to cmake.yml

Signed-off-by: Gabriela Gutierrez <gabigutierrez@google.com>

Author: gabibguti

.github/workflows/cmake.yml

@@ -33,6 +33,9 @@ on:
     - '!**Makefile'
     - '!**md'
 
+permissions:
+  contents: read
+
 env:
   CFLAGS: "-Wall -pedantic"
   # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)